AC3 is actually pretty disappointing. It's a good game, but I don't know, parts of it just didn't click. It's story was disappointing, it's characters weren't well developed, Connor was boring, there was no stealth, the ending was ass, and it was also historically inaccurate in parts (not that I care usually, but it's an AC game, and AC games pride themselves on being historically accurate).
I did love Haytham though, I wish we get a game with him as the lead.
It's still a good game, but I'd say it's the second weakest in the series after Revelations.