Super Meat Boy
If you like/love platformers, gotta check out Super Meat Boy on the 360 XBLA (and WiiWare+PC in Nov).
http://www.youtube.com/watch?v=aLXvQu-BaGo
Played the first world. It's hard but each level is very short, respawn times are almost null and the controls are spot on exactly.
Tons of fun and totally retro. Over 300 levels which include 5-6 worlds and each world has a dark world, that's uber tough. Multiple characters to choose from and only 800 MS points.
If you love tough games, you'll love this. If you don't, you still love it because each mistake is made by you and when you get past a level, you can literally go through it again super quick because you already know how to beat it. So basically, it's not cheap. Great game.