Assassins Creed series plummet in price after initial release. I saw AC:R on sale for like $30 during Black Friday. Same for CoD, actually. MW3 was also $30 during Black Friday, and the Best Buy I saw these at had 50+ copies of each.
I've never played a Hitman game, but i can vouch for Assassins Creed. AC3, coming out in October looks amazing so far. However, if you're into CoD more, especially multiplayer, Black Ops 2 would be a better choice.