I had waited over a year to buy and play Assassin's Creed II so by the time I had achieved the Platinum Trophy on that game Brotherhood was almost out. I decided that rather than risk series fatigue I would bide my time with Brotherhood.
It came out in November I think and I only bought it in January. As soon as I put it in the PS3 it didn't leave till it was done. I personally think it is a better game than ACII mainly because of the Brotherhood aspect. The ability to recruit a team of assassin's and have them do your dirty work was brilliant. Having a fully leveled team of assassin's appear out of nowhere and destroy your target is one of the best moments gaming has to offer.