Sonic Adventure 2.
Sonic Adventure 1 was crap, even ignoring the graphics glitches(and I played the gamecube DX remake version, with suppsoedly better graphics).
SA2 was the closest you can get to a good 3D sonic game. Not like the crap now. Most fans will say it sucked, but as much fun as the old games were, I always hated classical games. The difficulty was fine when that was all gamers played(and thus became pros, leading to games reaching impossible difficulties) but now it's just ridiculous. First level, no problem. Next couple levels? Can't beat them so easily.
A lives system and more focus on the Chaos Emeralds would have been nice, but even Mario had some changes going from 2D to 3D.
Overall, it was a fun game, but the difficulty curb when you unlocked the final few levels was horrendous. The game suddenly went Hardcore. And I still say the 3nd to last Boss Fight was pure torment in C++ form, meanwhile the true final boss was the easiest boss fight ever?
I actually had someone else beat the 2nd to last boss and it took hours. I beat the true final boss in seconds, once I learned how.
Still, I love SA2. Battle. Not that there's a big difference.
An obscure title my friend intoroduced me to my others friends hate, and is so obscure nobody knows about it: Freaky Flyers. Hilarious games. Wish I finished it. Difficulty curb was meh. Ever 3 levels you unlocked, you had to finish earlier, and once it gets to the WWII level, you have to come in first and man, it's like being punched in the face. You are lucky to make it within the top 3, let alone first. And there's still 2 more levels after it to beat. Consider the number of characters, and you just kinda drop the controller and hope the cutscenes at the end aren't something you're missing out on.