Galaxy On Fire 2 HD is a bit stuttery on the iPad 3 so that'll probably be nicer on the iPad 4.
NOVA 3 on the iPad 3 makes you choose between low resolution will full effects and full resolution with some effects missing. I expect they'll do an update that allows the iPad 4 to have full effects at full resolution.
Also Infinity Blade 2 currently runs at a lower resolution on the iPad 3 so I wouldn't be surprised if that gets a full resolution update for the iPad 4.
Other games that look great (but also do on the iPad 3) are Real Racing 2, Dead Trigger (crap game though - but free), Rage HD, Epoch and Shadowgun.