Perhaps he developed once his quest for revenge was over, but as a whole? Naw.needless to say, he was still a very charismatic and interesting character.
I have to disagree. Ezio isn't static once he goes on his revenge mission. There's a very gradual change in him over the course of AC2. You can see his motivations are becoming less selfish and more for the greater good. His quest for revenge doesn't really end until he spares Rodrigo in the Vatican.
Brotherhood's a different story, there's not much development there. But Revelations has good character development.