I got Assassin's Creed II the other day, can't believe I haven't gotten into this sooner! I'm absolutely addicted, I've spent hours and hours on it already. XD So much to do, so much to explore, I swear this is going on my 'all-time favourite games' list.
Hell yeah Glad you have seen the light lol. AC1 is kinda only good for the story as it's totally different to the following 3. I guess AC2 will leave you with pretty good knowledge of the story too though.
AC2 is my favourite of the 4 so far closely followed by ACB.
With out giving anything away ACR is a bit dull and misses opportunities to make it epic but towards the end it gets really interesting. Plus it shows how AC1 could of been if they had thought a little more and changed one thing.