I used to preorder a lot of games... I'm pretty sure back in '08, I preordered Gears of War 2, Left 4 Dead, Resident Evil 5, Fallout 3 Collector's Edition, Spore Galactic Edition, and Mercenaries 2...
I don't really do it as much anymore because I've got to commit to saving up for a game when I would rather just wait until it comes out and look at reviews for it instead of blowing my money on crappy games (Spore... how I wished something better could have come out of it...). I also preorder Collector's Editions because the stores often times don't carry them unless asked specifically by a customer for it. In fact, I got the only PC Collector's Edition of BioShock 2 that the local GameStop had because I preordered it. I'm also probably going to preorder the 3DS because I know it will sell out.