I'd rent Heavenly Sword. Yes it's fun, yes it looks great, but it's zilch in the replayability department. I beat it the first day I got it(day I got my PS3), started playing again a couple of days later, got bored and returned it.
If you've played NG or NGB already, skip Sigma.
Burnout Paradise just came out, but d/l the demo first to see if it's for you.
Warhawk is a great online-only game.