Before I go into a tirade that will be mostly flawed and I'll feel like an idiot after everybody points flaws out while belittling me and calling me a knacker, let's look into the past.
Specifically, the Dreamcast era.
It all starts with Sonic Adventure. Unlike Nintendo, who had a very good idea of how Mario should play out in 3D which shows with how Super Mario 64 was recieved, Sega wasn't so sure about Sonic's gameplay. 3D graphics in gaming was still relatively a new concept, and the main draw of Sonic was speed, which wasn't as easy to translate. Thus, Sonic Adventure, with its 6 different main methods of gameplay (along with lots of mini games, like pinball tables, snowboarding, and flying jets), was primarily testing ground for the gameplay. Was that bad in practice? Not at all. While the game wasn't solid, it was still recieved favorably and set Sonic as a force to be reckoned with in the new console generation. Any kinks could be ironed out with the inevitable sequels.
Sonic Adventure 2 appeared on the scene, and while it wasn't as vast an improvement as one could hope for, it was definitely still good, both relatively and over-all. 3 of the more monotonous/superfluous gameplay options (Sonic levels with flying and rubber banding AI rivals, Sonic levels but slower and with a heavier emphasis on puzzles and platforming, and fishing) were removed, and the 3 remaining gameplay options were "improved". At least, Sonic's stages were; the levels were made more streamlined, the controls were tighter, new mechanics such as somersaults and grinding were introduced, and a new character was added which doesn't really affect much except unique stages that have darker, forgive me for using this word, aesthetics. The other two gameplay modes were subjectively "improved": emerald hunting introduced more levels, and you had to hunt the Emeralds in a set order. Also gigantic space levels. Meanwhile, with Gamma dead, Robotnik and Tails were introduced as the new mech controllers, and the time limit was removed (though the usual 10'00 over-arching limit is kept). Also, the controls became clunkier, locking on became a pain, and if anything, it definitely felt like one was controlling a dumb pair of robot legs that didn't feel good. Also the unique speeding up was removed entirely and the levels became much more focused on platforming. Also, NEW mini games were introduced (the dumb racing, chao karate, and that's about it actually), and over-all the game was more linear with no hub worlds and only two stories. However, let's focus on Sonic's gameplay in each game, because let's be honest, people didn't buy the Sonic Adventure games saying "Oh man, I can't wait to control Tails in robot legs!".
Was SA2 an improvement? That's debatable, some people may say the more streamlined levels put a great emphasis on the speed and there were definite control improvements. However, I personally feel that a bit of spirit was loss, and the game started leaning towards letting the game play for you (while the grinding was really neat and a fun mechanic, it was basically just being stuck to a predetermined route and maybe hopping to a different one in a few levels). That doesn't mean either was bad, quite the contrary; there's a reason the two games were some of the best the Dreamcast had to offer (aside from there not being much competition of course).
Then, the Dreamcast dies, Sega gives up the console war, and Nintendo starts publishing Sonic games (though for a while Sony also got Sonic games, except for the original 2 Adventure games oddly). Now we enter the latter half of the Dreamcast era:
Sonic. Heroes.
I hate this game. I hate it like I would hate a person who gave up a great opportunity because they felt better ones would come eventually. Yes, I played through it. Yes, it was my second ever Sonic game (after Sonic 2). Yes I eventually got the full final ending.
I don't hate it as a game. It's not horrible, and can be enjoyable if you try. I hate it because of what it started.
At its core, Sonic Heroes could've been the Super Mario Galaxy and rocketed Sonic into greatness. The levels? Absolutely beautiful, and all unique, especially hard considering how many level archetypes had already been used in 3d Sonic games. Giant beautiful sea with a bunch of islands and giant turtles? Hell yes. Carnival-esque Casino with a bunch of cool attractions? Giant Airship Fortresses,b eautiful green jungles full of giant wildlife, metropolis-like cities. Not to mention how much Sonic Team obviously referenced the classic 2D titles. A more cast-focused story, with the return of Metal Sonic, now as a bigger bad than ever before. Levels with 2 acts and a boss, the bosses usually being infinite runners. Classic mini-game infinite runners to actually get the Emeralds instead of receiving them as the plot demanded.
But then some idiot looked at Super Mario Sunshine, and went "Oh, that game's got a unique mehcanic and is successful, we should add a gimmick to our next game to!"
What he forgot was that not only was the FLUDD mechanic well thought-out, it wasn't even that big a change, just a simple new set of physics and a new abilty to defeat enemies, by spraying them with water. Plus let's not forget how Super Mario Sunshine, while it did well, was nowhere near as popular as Super Mario 64 or the eventual Super Mario Galaxy.
Thus, team action was born. Doesn't sound that bad, right? Knuckles Chaotix got away with it without it being too much of a pain, and hell why not even give that game a nod by re-designing the characters and adding them to the roster? Awesome.
Here's all the things Sonic Heroes did wrong, because I got stuck here and didn't know what else to write to lambaste Sonic team.
Knuckles Chaotix had teams as a concept, but you could choose from a few characters, each with unique abilities, and the gameplay was otherwise pretty much unchanged from other Sonic games except for the characters' respective abilities being introduced. Sonic Heroes, however, just said "**** that, let's throw 4 teams in", and made them all no different except for very minor changes (I'm going to refer to each team by their leader unless otherwise noted because I don't like typing out each team's name):
- Sonic and Shadow can ring-dash, which is never actually used as a mechanic.
- Amy can slowly descend instead of just falling by holding jump in mid-air(even though Flying or even actually floating exists in the game already making it more than useless).
- Espio can permanently stick to walls when Triangle jumping, which not only pops up as an actual mechanic about 4 times throughout the game as a whole, but the sticking is never used as a mechanic in itself. He can also turn invisible, which is an actual mechanic twice at the most (I know it's used once, but otherwise I can't remember).
- Sonic's Team Blast just kills enemies and can stun bosses. Shadow's Team Blast is Chaos Control, which freezes time for 10 seconds. Amy's Team Blast destroys all enemies and makes you invincible. Espio's gives you rings based on enemies killed and is also admittedly pretty goofy and cool.
- Knuckles and Omega shoot their teammates like cannons as mid-air attacks. Big and Vector bounce instead.
- (also Knuckles is small unlike other Power characters)
"Why not give each team a unique story where they intersect and fight other teams?"
"Sure, that sounds cool, but we only have enough levels for one full story."
"Just give them all the same levels in the same order and maybe make them shorter or longer depending."
It's the same game 4 times in a row, with incredibly minor differences between each playthrough:
- Sonic's levels are just normal.
- Shadow's levels are a bit harder, and he gets tougher enemies.
- Amy's levels are shorter and she also has a tutorial level before the actual game.
- Espio's levels involve doing some sort of mission each time.
- The bosses are all the exact same. The only difference is how much health they have.
The team mechanic itself. It's stupid. Spindashing is useless because they made it some weird team shoot thing that doesn't even go much faster relative to normal running. Flying parts are just mashing the A button and hoping you don't run out of "Fly power energy". The power mechanic is ok, but for a game series that's all about speed, especially in this game where momentum is ramped up tenfold and levels are incredibly linear, stopping to fight a few enemies and open up a door is an annoyance at best. There's no deep gameplay related to the Fly or Power formations, as the levels are obviously designed with just the speed characters in mind, except roadblocks are added in to make you switch your stance every once in a while.
Oh yeah, and sometimes the game just flat out won't work. Loading times are heinous, there are rampant bugs in almost every level, and some levels are almost impossible to play without experiencing at least one "oh you're dead for no reason" glitch, like the grinding just not working some time. Also the camera is ass.
Sonic Adventure was an okay game. While there was a lot of filler, and most of the extra gamemodes weren't very enjoyable, as well as the story being nuts, Sonic's levels were still super fun to play and speedrun, and he has the most levels, lacking only one level that other characters also had (there were around 12 levels and each level had at least 3 characters that appeared in it; Sonic had a whopping 11 playable levels). Sonic Adventure 2, again, was an okay game. The treasure hunting was somehow made worse than how it was in SA1, the mech levels took everything unfun about the Gamma levels in SA (which were probably the second best levels in the game after Sonic levels) and attached a super annoying loud buzzing sound whenever you locked onto enemies, and the story was even more crazy than the previous, but now you got two times the Sonic levels, and they were all just as fun, if not more fun, than the SA1 Sonic levels.
If Sonic Team had kept the "Don't fix what isn't broken" mentality going into Sonic Heroes, we might've had the Sonic Generations of the Dreamcast Era. Imagine it: the Sonic Heroes levels, but instead of 3 characters at once, you're only playing as the speed characters, with every bug fixed, and no more roadblocks to ruin the superspeed feeling. Infinite Runner Bosses and somewhat linear but still complex levels, just like the original Sonic games.
Sonic Heroes got the whole "innovaton" ball rolling, and was continued with Shadow the Hedgehog, which at its core was another Sonic game except the controls were even worse than before, and guns were also a thing. Also, vehicles were added, the very definition of superfluous. Everything was going awful because Sonic team wasn't sure people would accept just plain old Sonic up until they did good with Sonic Colours, and then Sonic Generations and things seemed brighter for at least a moment, until Sonic Lost World because "nah another game like Sonic generations in spirit will never sell, we should try Super Mario Galaxy but with Sonic!". And then Sonic Boom.
At their cores, Sonic Heroes and Shadow the Hedgehog, and hell, even more recent games like Sonic '06 and Sonic Unleashed, were the 3D sonic games that could've been great and kept Sonic from becoming a laughing stock. They had everything there: beautiful graphics, unique levels, and amazing music (luckily the music wasn't mulled down by ****** mechanics, contrived storylines, and bad controls). Sonic team was just too self-conscious to try and go for it, so they had to pile stupid gimmick upon stupid gimmick until the whole ****** trash heap that is the Sonic series came falling down on their heads.
In conclusion, please watch this video to get a good idea where I'm coming from.