Of the games I own, Wipeout HD and Killzone 2 are definitely better in 1080p. Uncharted also looks a bit better but not by much.
THe thing is, you buy an HDTV today, most of the products (games, movies), as well as tv shows, are native 720p, so you won't notice a lot of difference. But it will change in the next years, and if I buy a TV today, I certainly buy it for the next 5 years at least, so might as well be prepared.