Sonic Adventure 2 was not better than Sonic Adventure. Many see this as the game where everything started to suck but most of them can't put into adeque words just why beyond "It's not like the classics". While that is correct, this situation needs specifics if you really want to get that point across.
This game goes back to the Act to Act formula seen in the classic games which is something I prefer. Act then cutscene to move the story along, this is preferable to the hub worlds where one can get lost and not know what to do. It is less of an issue in modern day game design but for just Sonic games, this is what I prefer. Unfortunately, they kept the multiple characters but made it worse in that you switch characters from act to act. This is bad because this stops the player from learning from level to level, it makes the difficulty scale erratic in that the player doesn't get the time to improve on a given playstyle. How can one get good at Sonic levels if you switch to shooting in the next act? While I am an advocate for players to "Git Gud", they aren't able to because of the shift. It's like being forced to to learn Math, Science, and P.E. in the same class where you don't know what kind of question the teacher is gonna ask next. Speaking personally, there should have only been two playable characters: Sonic and Robotnik.
Now, another comparison to Sonic Adventure is the level design. Sonic Adventure 2 has shifted into a much more arcadey design which relies on memorization instead of skill. This is encouraged by the new ranking system and does work for what it is. Homing attack chains and Light Speed dash paths make up the various shortcuts. Emphasis on "Shortcuts" as these replace the alternate paths seen in previous games and is the "simplification" you will see people argue about. The shooting gameplay hasn't changed granted the mechs are far clunkier than Gamma (realistically so). The treasure hunting hasn't changed but the radar has been nerfed for some reason. If you hated shooting and treasure hunting before, you'll hate them even more now that they aren't semi-optional and aren't just retreads of Sonic levels. That's a point of contention, in Sonic Adventure it is clear that almost every level was designed with Sonic in mind first with other characters just using modified versions of his levels. This is a great bit of efficiency (especially in comparison to say Sonic Forces) and a great way to handle multiple characters. In Sonic Adventure 2, the levels are all mostly original meaning those who hate alternate playstyles can legitimately complain about resources being wasted. To use the Hero path as an example: Six sonic levels, Five Knuckles levels, and Four mech levels. This is made worse by the simple fact that Knuckles has no reason to be in this game.
On that note: the story is trash. Given the option of No story or a Bad story, I prefer the former. It's also rather telling in that this is the era where Super Mario Sunshine goes full Jerry Springer with its "Mama Peach" storyline and somehow Sonic Adventure 2 managed beat it by going full retard by Sonic possibility killing several people in the opening cutscene. I could go on but I can forgive a stupid story if the gameplay is at least good which it is. A bad story is an easy thing to fix in the grand scheme of game development, it's not a fatal error. I will state though that Knuckles and Amy have ZERO reason to be here and that Robotnik's campaign story at least makes sense.
Playable Eggman was something I never knew I wanted. Shadow and Rouge I'm pretty indifferent to. I enjoyed fishing as Big, so I was bummed he was gone. I was glad to be able to see his cameos in my initial playthrough at least. I will forever be disappointed by the lack of Amy Rose. It's nice that she was in the Battle multiplayer, but that wasn't good enough. Overall though, I enjoyed all the alts you could use in multiplayer, and frequently mod them in for my Steam playthroughs.
The music was on point of course. Jun is always great, and Fumie really shines here again. Chao garden improvements were fantastic. The story was fun, but really lacked the menace and punch that made Chaos (and Eggman's doings) really pop.
The game and its update were one of the last great Sonic games, until recent years, but will still always be (mostly) overshadowed by its predecessor.
Overall, still a good game but not as good as its predecessor.
Sonic Heroes is a game I find myself going back to from time to time. It's what I want in a 3d Sonic game though admittedly could use a good deal of refinement.
It's aesthetic is aiming for the Classics (as stated by Iizuka in an interview), the story is simple (though they have stated it was shoehorned in at the tail end of development), the levels are all Sonic levels with some Tails and Knuckles gimmick peppered about for multiple paths, special stages are back (this was before they started reusing the half-pipe to death), and all the RPG elements have been given the boot. Yes, we are on the right track.
On the downside of things, character movement has gotten worse, specifically Sonic who can reach top speed without slopes or a spin dash with a too strong rate of acceleration making him hard to control. This was the beginning of the "Make Sonic as fast as possible" philosophy bleeding into the 3d games (Sonic Advance 2 came out a year ago). Knuckles in comparison is too slow which is confounded by his punch movements being imprecise (hence why everyone just uses his fire dunk). Tails doesn't have any movement problems but his "Dummy Ring" attack is just terrible. All these things could have been fixed with just one or two rounds of playtesting (assuming they didn't tie all this into Renderware's physics engine).
Levels at the time were criticized for being "too long" in that it'll take you about 5 mins to beat each level without dying...Boy how times have changed. People say that the levels "get worse" as you go on but I don't see this as the case. Only levels that are trouble are the Airship levels which are hard but they are the last levels, they're suppose to be hard. That said, there are more death pits in the later levels, mix this with a hard to control Sonic or Knuckles' imprecise punches and I believe this may be the cause of people's frustrations.
The major complaint heard is "there are too many characters" which is another case of "Don't make other characters mandatory". It's the same problem Sonic games have in that Sonic Team keeps trying to pad them when they don't need to. Megaman 11 came out with NOTHING added to the main campaign over the earlier entries and nobody's the wiser. Were the characters just unlockable extras (which would make sense seeing as how they play mostly the same as Team Sonic, and Team Rose would realistically be trash), nobody would be complaining. Hell, this game has chaos emeralds which should be the only requirement for unlocking the Super Sonic Fight.
Despite all of this, if you were to ask me if this was better than Sonic Adventure 2, I'd have to say no. Having bad character movements is a fatal error which will drag down the experience moreso than a bad Story where Knuckles clearly lost his virginity at the end of it....Also Sonic Adventure 2 has a chao garden, you can't compete with that.
I LOVE Shadow the Hedgehog for all the wrong reasons. We've hit "So bad it's good" territory.
If you hadn't noticed, the games have gotten progressively worse since Sonic Adventure culminating with Yuji Naka's departure with Sonic 06. This wasn't Sega's fault (at least not entirely) because their other games at the time (Shinobi, Otogi, Panzer Dragoon Orta, Jet set Radio Future, Gun Valkyrie, Crazy Taxi 3, Nightshade, Super Monkeyball, F-Zero GX) were quality games. Something happened at Sonic Team which we'll never know the full details about. It makes for some interesting speculation at least.
Anyway, Shadow the hedgehog is an awful game. Character movement is still awful (though ironically, they have a "Strafe" button that can be used to stop on a dime which makes platforming easier, I don't think they intended that), the gunplay is weak, despite being a "spin-off" Shadow plays exactly like Sonic + Gun, Levels are blatantly recycled to a point where you can pinpoint exactly where sections of levels are copy pasted, the multiple endings aren't satisfying, the story sucks, the localization is incompetently racist (Black Aliens when just saying Aliens would work just fine), and the multiple missions in levels just aren't fun (even the kill the president one).
The ONLY reason anyone ever plays this game is to talk shit about it because playing ain't fun. Things that could be fun or interesting aren't given enough time. They wanted to do everything and did so incompetently. Even the things I feel like defending about this game aren't worth defending. Unlike Sonic 06 where the game is a technical failure, Shadow the Hedgehog tanks what could have be a viable spinoff franchise entirely on its own merits.