Electronic Arts just released an iPhone version of its NBA live game and claims it to be the:
Most realistic 5-on-5 action available for iPhones and iPod touch
Not hard to claim since there aren't many other Basketball games on the App Store at the moment...
It features the authentic NBA teams and players and comes pre-packaged with 15 soundtracks from artists like Snoop Dog and Xzibit. All those goodies don't come cheap as you'll have to spend the classical $9.99 that EA sports charges for its games.
I personally find these kinds of games hard to play using on-screen controls, they are designed to be played with a console controller and it's just frustrating in the end.
[on the App Store]