galcon or icopter
there isn't a better game out there on the iphone in terms of replay value and pick-up-and-go. other games either fail on the entertainment level or require too much time playing, thus greatly depleting your phones battery....which, the point of a phone is having battery power so you can send/receive CALLS.
if you wanna play engrossing games, the iphone shouldn't be used.....get a psp/ds/ps3/xbox/etc. why people spend so much time on an iphone depleting their batteries is beyond me. not to mention, the more you play those games *cough* enigma *cough*, the more your battery wears out and reduces it's overall life cycle.