Yes, you can predict whether or not a game will be good or not. But putting money on your prediction is the very definition of gambling, and that seems like a pretty ridiculous course of action when the only thing you have to gain is the ability to play the game a few days/weeks ahead of time. And don't get me started with "exclusive DLC" and every other carrot-on-a-stick scenario publishers are spewing forth in efforts to sell copies before the masses realize how shitty the games are. A game is supposed to be its own incentive.
Exclusive weapons! New maps! Bonus Experience! Beta access!
Quick, preorder now and secure your very own spiked dildo to be rammed sideways up your ass on release day! Supplies are limited!