My favorite time-waster is The Blocks Cometh by Halfbot. Fun little indie game. The only true adventure game i played was GeoSociety, the closest thing to Pokemon on the app store, it's pretty good in my opinion. A few others are Osmos, a great strategy game, Hook Worlds, a classic arcade grappling hook game, Melon Golf, used to be one of my favorites, simple but fun golf game, Contre Jour, strategy game with a fair amount of levels, never got around to finishing it, and the only free one I have to mention is Solomon's Keep. Sadly I got it when it was paid, but it's pretty fun. If you enjoy that, I suggest getting Solomon's Boneyard as well.