Sonic Generations, an amazing game! I love the game. HOWEVER... I have one complaint: The physics are wacky. And it's very noticeable when trying to ear one particular "Greased Lightning" trophy/achievement.
That's the 'Beat Green Hill Act 1 in under a minute' one, right? I remember having a hard time with that one, but I got it eventually. As for the physics, I noticed it with Classic Sonic, and if there's one thing the 3DS version has over the console versions, it's Classic Sonic's physics.