The only games I own that require 1gb+ installs are MGS4 and Heavenly Sword. I know it's purely coincidental, but I like that my tastes (for the most part) coincide with my want to save space. :P
I'm sure Resistance 2 and Killzone 2 won't require much of an install just like the rest of Sony's internally developed games from SCEA and SCEE as well. From what I hear, the same goes for LBP. They've managed to heavily compress the size of downloadable levels (i.e., items you created/importedyourself as opposed to stuff that comes on the disc, like pictures) to save space as well.