I was working for 1UP when Assassin's Creed came out. I'm not sure if you remember the EGM scores for that game, but it was all over the place. Some people loved it, others hated it, and it caused a bit of a thing for a while there.
Scared off by the mixed response, I ended up skipping over the first one, but then picking up Assassin's Creed II based on the incredible word of mouth--and loving it. I really dig the fiction, too, so it bothers me that I don't know the foundation from the first installment.
Given how far the mechanics jumped from the first game to the second game, however, I'm not sure heading back towards Assassin's Creed would be a very satisfying experience. What say you?