There's more Desmond in Revelations than any of them. You learn a lot about him, his upbringing, how he ended up where he is, and how he's connected to the Assassin Brotherhood. I'm not really sure what HC is talking about when he says it's a different story and you don't learn what happened. They only spend the whole game talking about the end of Brotherhood. But yes, it does also serve as the conclusion to Ezio's story, as far as the games go anyway (the CGI film Assassin's Creed: Embers actually shows the end of Ezio's story).
But it, like all the others, ends on a cliffhanger as well. We won't know what the hell happens until Assassin's Creed III. I'm really interested in how they're going to end it with the whole 2012 Doomsday thing since they're making it a point to end it before that date actually comes.