Brotherhood Not Really Ezio's story
Brotherhood put a lot more of the focus and character development on other main characters like Claudia, Macchiavelli, Rodrigo, Lucrezia, and Cesare, ect. On the one hand, having Ezio in near permanent "I know exactly what to do next, and I don't care if you don't understand, just shut up and go with it" mode showed us that for once, Ezio is completely within his depth.
In this game Ezio is the BA guy who saves everyone's butts by knowing french, understanding Minerva's message, knowing when to use the apple, understanding how to get the factions of the city together, and generally being able to hold off 50 highly trained guards at the same time using only a sword.
This kind of thing used to be left to La Volpe and Mario and the like in AC2, but in this one, Ezio helps La Volpe overcome his distrust, Mario is shown to be not so invincible after all, Caterina has her own story arc.
As for the villains, Rodrigo becomes more reserved and secretive as Cesare grows out of control, and the entire empire he's built for himself separate from the Templars is eroded by Ezio and his order. Cesare also feels the sting of this, but instead of quieting down, he gets more and more filled with rage, finally becoming maniacal.
Lucrezia attempts to keep Cesare focused on her, but finds that he never truly cared about her. Later, Ezio teaches her that she needs to learn to stand on her own two feet, instead of relying overmuch on men who don't care about her.
Ezio is basically the foil to all these stories, he's even the foil to Desmond's story, which has more character development for Desmond than it does for any of the other characters in the game.
This is one of the reason I'm not completely tired of Ezio. The last game didn't really seem to be about him. I'm hoping that this changes as he enters a more hostile environment and the focus of the story is shifted away from desmond and more onto both Ezio and Altair.
Agree?
I'm with you. I'm not tired of Ezio at all. I'm also excited about Altair being a playable character. I know I'll get hammered for this, but I couldn't get into ACI (although I never attempted it until I had completed AC:B). I didn't like the gameplay, the graphics, or Altair's movements. If I had played it first, I probably would have loved it, but I feel that ACII & AC:B had a better storyline, graphics, and Ezio's movements were much more fluid (which we would expect from a master Assassin). I'm looking forward to this game a lot.
Never mind, I found it 
AC 1 felt too glitchy for me, and some design choices were really weird. but I did like how the assassinations were totally open. I just hated ALL the stuff I had to do to get to them.