While I may still have found it tricky, I still thought it was very same-y. The traps were rather repetitive, and it was just a generic level layout.
I always felt like Perfect Chaos was a little underwhelming. Understand, I didn't get to finally play Sonic Adventure until I played SADX in 2004. I had always heard of Perfect Chaos and seen pictures, as well as reading the Sonic Comic, etc, so Perfect Chaos had been built up as a fearsome, climactic battle in my mind. When I finally got there after enjoying my way through half the character stories and slaving my way through Amy, Knuckles, and Big, I was... underwhelmed. I don't know what exactly they could do to improve Perfect Chaos (I did not play the Generations version, I should probably get to that), but it never quite felt like it measured up to the apocalyptic proceeding cut scene or how terrifying Chaos was to me.
I'm gonna have to echo everyone who's said the Time Eater. Really, it was one of the only disappointing things in Generations. The execution was horrible because the boss arena was basically a mess - it's so hard to see the rings, and don't even get me started on that achievement where you had to beat the Time Eater without taking a hit (that took an age for me to get because it's often so difficult to see what's going on). I think a lot of the more recent Sonic bosses have been let down by the fact that they're essentially Mushroom Hill's boss in 3D again and again. I mean really, there's only so many times you can do "let's chase Robotnik" until it starts becoming stale. At least with this style of boss in Generations there's a bit more variety to it.
The last boss of Sonic 4 Episode 2. I was expecting a hard gruelling battle and it ended up being the nearly as easy as the first one. It was also a naff version of the first boss of Colours.
The last fight against Robotnik in Sonic Adventure 2 should have been an actual Robotnik fight. Not running around in a cirlce until he comes into your sights. I would have even taken playing as Tails/Tornado, as long as Robotnik was in some sort of giant robot. The other rival fights were good, though. Also, pretty much every boss from Sonic CD.
This. SA2 never has Sonic fighting Robotnik thanks to that rival system and it's quite disappointing. Where's the giant mech? No where.
Time Eater was doubly disappointing and a real let-down considering how awesome the game was right up till that point. The pointless little platforming section in the hub world didn't help, either. I know there's a need to build some tension before the ultimate fight, but yeah.
On a slightly related argument, if you're gonna put a pinball level in a game, make it: A) behave properly, like a pinball should. B) not make it fucking suck. (see: duke nukem forever) Understanding the games physics is not the problem, expecting a different genre of game to operate on your "designed for high speed platforming action" engine fucking is. The SCD pinball sucks. everyone knows it does, OK it's the best they could do with the engine they had, but it still sucks. anyone who slags it should not be subjected to a wordfilter because sega are fucking spastics.
I don't see why you'd want giant mechs, since Eggmobiles are more interesting. People complain about not having bosses every zone anymore, but you've got to understand that the bosses are much more complicated now. Most of the Sonic 1 bosses had one, or two attacks and lasted under a minute. You could have a boss every zone, but it would have to be simpler. To me, that would be a plus since I don't really enjoy bosses that drag on. Egg Dragoon!
In Sonic Heroes, I've never beaten Egg Albatross with anyone but the speed character. As shoddy as the team system is, if you're going to make it your gimmick, make it your gimmick. Don't force me to fight a 200 HP boss with just a homing attack, occasionally getting hit with bullets and falling to my death in a pit between the two paths.
Sonic Colors, half the bosses are literally just fighting the same boss you fought 2 levels ago over again
Indeed, the boss may have been decent, but with such a mega fucking awesome sprite, it was terribly underwhelming. It needed more lasers, lasers make everything better.
I'm gonna go out on a limb and say a lot of the Genesis-era bosses came short of their potential. With a few exceptions, most of them feel like afterthoughts tacked on to the level, with static, unchanging patterns. Even something as minor as having them speed up every 2-3 hits would make them a lot more challenging and interesting.