Doodle Jump
A simple game deserves a simple review:
Doodle Jump is the ideal micro-game: small price for a small game, aside from being a small game content wise, it can provide hours of entertainment as a simple time waster. Since you probably carry your iPhone or iPod touch with you most of the time, it's always within reach even when you are doing something incredibly boring, like waiting in line.
A hardcore casual game, Doodle Jump is nothing if not simply amusing, it won't replace Halo, but it'll suffice when you're on the train or waiting for a pizza. It's hard to rate it on the same scale I used for Persona 3 and The Red Star mere hours ago, but I definitely think it deserves a perfect five.