This hasn't been mentioned yet, but...
MLB '09 The Show is a gorgeous looking title that really shows off the beauty of HD gaming. Yes it's obviously not the absolute best but nonetheless it has some pretty stunning visuals, IMHO anyway.
Definitely agree though, Dead Space, MGS4, Uncharted, Killzone 2...etc..are all amazing titles - kinda nice to know that there are some many of these A+ titles available now.
"Huh, I thought the rocky mountains would be a little rockier than this....that John Denver is full of s#!t man!"