Sonic Adventure XBLA is a pretty lazy port. But they're is still a LOT of fun to be had!
So you play as 6 different characters. Sonic, Tails, Knuckles, Amy, Big, and E102 "Y". Each character has their own unique gameplay style, with the exception of Big, who just plain sucks.
Sonic's gameplay is easily the best, run to the end of the level as fast as you can. It's fun, addicting and you can do it anytime. Tails's gameplay is good, you for some reason just race Sonic to the end of his levels. Knuckles flies around collecting pieces of the master emerald. Amy's feels similar to a Mario game. (Play it and you'll see why). E102 is a shoot em' up with a time limit. And Big's... forget I said anything.
All gameplay is fun. (except for... you know who.)
The game doesn't really add much, except for online leaderboards, and Sega kinda scammed us... The main game is the Gamecube version of Sonic Adventure, but without the DX features. And to get those it'll cost ya another 5 dollars.
So, if your a die hard Sonic adventure fan, there is a lot to love.
Pros: Fast and Fun Gameplay, Leaderboards
Cons: Ugly visuals, nothing new added, Horrible camera, Characters look hilarious when they talk. Glitchy as heck. Big the cat...