For those of you who are interested in catching up with all story details from ACI, ACII, ACII Brotherhood, and Revelations, game spot put together several videos that have all the cut scenes for each game. Each game is divided into 5 videos. It's almost like watching a tv min-series since each episode is about 30 minutes long.
I've been watching these since yesterday to prepare for 3 since I didn't play Brotherhood or Revelations and I wanted to remember some key details from the first 2. LINK
The above link is set for episode one of ACI, but you can find the set of videos you want by looking on the right menu. Just click the picture of the video you want.