Spider is a great puzzle-platformer game with great controls
Wolf RPG is great
Civ Rev is great
Real Racing is great, easily the best racing game on the device and plays a bit like PS1 racing games
Sway is a platformer where each side of the screen controls the left or right hand grip, and using the momentum, you have to toss yourself through the level
Space Invader Infinity Gene is great
Minigore is sorta good because it's the first iPhone game with on screen analog sticks that work. It's a twin stick shooter. Good graphics, too.
There are a bunch more. Rolando 2 is great too. One thing to watch out for are people who are more interested in the iPhone as a device and not for the games. Like, "Rolando is better than LocoRoco" or something when they don't play similar. Rolando is a puzzle game, LocoRoco is more of a platformer. (I'm not big into either of the series)
Flight Control is super-cheap.
the CO-OP guys (ex-1up crew video show) do a great job of covering iPhone games. Seeing them in motion really helps with some of the wackier concepts.
the problem with the coverage of iphone games there is that they never have complaints for these games because they're "only $5" or something. They covered Gangstar, which is garbage, and praised it for the novelty of seeing a GTA-like game on the system.