While the AppStore does have a games category, it is very large and iPad games are thrown in with those for it's smaller stablemates iPod/Phone. Many of which are of dubious quality. Frankly the store could do with some serious restructuring.
Might I suggest you check rather with some websites specialising in games apps and check out reviews first.
Sites such as Touch Arcade and Pad gadget etc..
Also there are a few threads on this forum regarding peoples favourite gaming apps.
Hth.