The games I have on my Iphone are:
Super Monkey Ball - Loads of fun
Sonic 1 - Fun but controls can be a bit awkward
MGS Touch - This is pretty dire and I wouldn't waste your money on it. It's just tapping on the screen to shoot things, No sneaking or anything like MGS franchise
Flight Control - which as mention before is pretty addictive once you get familiar with it.
Icopter - This is the game i've played the most. It's nice and simple but gets addictive trying to beat your highscore. Always good for a quick bash when you have some time to kill too.
Fieldrunners - This is pretty much tower defence so if you like that you'll like this.
Also got Imobsters which is ok just like mobwars on facebook and of course Bewjeweled2.
Edit:// I Also did have blocked which is a really good puzzle game that appears to of deleted it's self off my phone which is annoying seeing as I had nearly completed all the levels GRR