Euphoria14 on 11 April 2009
Fable 2 is the only game I would really recommend for you if you are looking for an RPG.
If you just want something cheap I would go outside of the RPG genre and take a look at Bioshock.
It is a really fun game and one playthrough will easily net you 600+ gamerscore. 
iPhone = Great gaming device. Don't agree? Who cares, because you're wrong.
Currently playing:
Final Fantasy VI (iOS), Final Fantasy: Record Keeper (iOS) & Dragon Quest V (iOS)
