I have just completed AC2 again and still can't understand how people can say it's better than 3 or that Ezio's a better character. Almost everything about it is worse than 3, it was just repetitive, boring and frustrating (I still got 100% synch and got all the achievements though). The story is just : kill him, follow him, kill them, etc.; there's no plot (until The Apple makes an appearance), there is basically no Desmond story unlike in 3, and Ezio is a terrible assassin. He's arrogant, childish and selfish; he's only killing those Templars for revenge, not because he understands The Creed and what the Templars are doing is wrong. He only wants to be an assassin because it's an easy path to finding those that killed his family; even when he defeats Borgia at the end, the only thing he mentions is his family, not that he's stopping him because he believes that what The Templars are doing is wrong.
Connor, however, is mature, deep, philosophical and understands the true threat that the Templars pose (as he makes clear when he kills them, which Ezio doesn't). Connor is the first true assassin (Altair didn't have a clue what was going on, so doesn't really count, he was still better than Ezio though). You might like Ezio's bad-man attitude better, but you can't tell me he's a true assassin like Connor is.
I'm in the process of researching the games so I can right something which will hopefully convince you all why 3 is better. I'll try to be objective, but ultimately games aren't. However, I doubt anyone would be able to defend 2 when they realise the true differences, that I will make clear.