the (paid-for) games I still have on my iphone are:
- Blackbeard's Revenge (like puzzleloop/zuma)
- Cro-Mag
- Dizzy Bee
- Galcon
- Solebon
- Vay
The two I really recommend are Blackbeard and Solebon.
Blackbeard is the best of the bunch in terms of design, polish, and just plain fun. The problem is that I've already beat it on the hardest level and there's nothing to do now but wait for the developers to release an update (they say one is coming). If you haven't tried it, you really should.
The one that I really reach for most commonly is Solebon. Yeah it's just solitaire, but it's really well done and there are tons of games (I used the free "sol free" for a long time, but for $1.99, get the 25 extra games. It's so worth it.).
I'm actually not a big fan of the accelerometer games (cro-mag, dizzy bee). They are fun for a while, and both of the two I have are good games, but I just tire of them more quickly. I don't really know why.
Vay is pretty well done too, but an RPG like that just isn't all that well suited to a 3.5" screen. (I'd still buy the original final fantasy if they ever ported it to the iphone though!) Also, all the navigating through menus takes a while and makes me feel like I'm using a blackberry.