I try to play the first but its not interesting for me at all.Play 10-15 min and delete it.The new games are not good at all.Or some multiplayer with friends are better.

AC is simply the best i am so addicted to it, the action, the story and the weapons, omg 0_0 didn't like the first one though, to much repeatable and to much long cutscenes

The first one was too repetitive,gameplay-wise.
Ezio's saga brought some fresh air to the franchise up until Brotherhood,since Revelations felt more like a filler.
The third one was a major letdown,trees and snow can't compete with Venice,Florence or Rome..And the fourth one will probably go down the same path.

I'd say the first one was quite a disappointment because of it's repetitive gameplay though some things were quite fun; like combat and assassinating randomly people (i liked that).
Well then i got ac 2 and I was excited and it was daymn cool with a story that was nice to follow.
And then I got ac 3 (on pc this time, other two were on xbox). I didn't care for Brotherhood or revelations because i felt like I got enough of Altair and Ezio. Then came Connor who was certainly a interesting character. I kinda liked how you were able to move almost EVERYWHERE!

For me Ac3 takes the lead here. (Also the combat system in it feels good!)

I love the assassins creed games, my personal fav is ac 2, I have ac 3 but I think that is too slow moving in terms of the campaign, and unfortunatly the multiplayer is very weak.