Nova 3 and Modern Combat 3 are both great. In the case if Nova 3 though, it can't cope with doing all of the effects at full resolution so you have to choose between the full resolution with some of the effects missing and the iPad 2 resolution with full effects. IMO it looks way better with the full resolution.
If you decide to go for any of the Asphalt games, Asphalt 6 looks great and runs in full resolution, but Asphalt 7 runs in a lower resolution so you might want to stick with 6.