Been downloading and playing quite alot of good games on my iPad recently and thought I'd share the best. Good time to do it as there's some big sales on at the moment.

Dead Space - pretty much like the pc/console versions, excellent graphics especially on the ipad2 (heavily reduced at the moment)
http://www.gametrailers.com/video/ipad-gameplay-dead-space/709840

Street Fighter IV Volt - this new volt edition has online play.

Starfront : collision - RTS that plays very much like a mini starcraft, has 3 races and quite a few maps. Having alot of fun playing it online. (heavily reduced at the moment)
http://www.dailymotion.com/video/xh1tgs_starf...videogames
Works and looks even better on the iPad.

Land Sea Air Warfare - another great RTS but this time more akin to Total Annihilation and being able to show many more units (250-1000) works and runs really well. Has a random map generator too. The only problem is the whole game is based about skirmishes against the A.I. which works great but adding a multiplayer mode would be amazing. Read that the guy is still working on it though so hopefully mp will be added. Also on pc and loads of other devices.
http://toucharcade.com/2010/06/06/land-air-se...be-missed/

Icarus-X - pretty nice and cheap Shoot em up

Danmaku Unlimited - another nice bullet hell shoot em up.
http://www.nineoverten.com/2011/05/28/danmaku...ell-shmup/

Mostly playing the Starcraft clone at the minute, online. Just waiting for an update to 'land sea air warfare' as it's going to me epic if they add multiplayer!