Apple has a list of suggested apps for the new iPad, but this includes some apps and games (admittedly very good ones) that don't yet support the Retina display.
So if you're looking for some high-resolution Retina-display app action, here's a list of apps to check out. (Note: all links open iTunes).
A new update to this classic hack-and-slash adventure game now includes Retina display support. It already looked incredible, so the new iPad version is outstanding.