Hitman for sure, since I never enjoyed the AC games (they're boring).
Absolution, while a solid stealth game, is not for everyone. While I'm only on the 4rth mission right now (out of 20 missions?), the game almost forces you to play a specific way. It's more lenient in terms of getting spotted compared to previous hitman games, but at the same time forces you to do specific activities (that are not told to you) to get highscores, so you'll spend about i'd say 50% of your time walking/running around to find out the best possible way to beat a mission. Of course you can beat the mission any way you want, but finding the best possible way to get the highscore takes a while. So far I'd rate it 7.5/8 out of 10.
I'd recommend other games instead, such as dishonored (recently released) or mark of ninja (if you have a decent pc), b/c those are stealth games you might like more. Deus Ex (ps3/pc/360) or Splinter cell conviction (pc/360), are great stealth games as well. These 4 games listed are all fantastic stealth games, so take you pick.