I just played about 2 hours of AC2. I was trying to replay the first four games in full before AC3 but the first one is too repetitive. I'm only about halfway through 2 so I don't think I'll have enough time to finish AC-B and AC-R before the 30th. I just have too much stuff going on.
Although, 2 is the biggest game, with DLC.
2 is still the best of the series, IMO. At least for another couple weeks. For me, having a big, interesting sandbox to explore is as important as story and gameplay- and 2 has the best world of any of them.