I'll be honest, while it's a very, very good game, it wouldn't be the best game I've ever played. It's got great interactivity and great story, but it's more like an interactive movie than it is a game... the puzzles are ridiculously short, and the gameplay is kind of watered down. I could probably get through most of the fights with just the basic arrow and basic pistol (on normal). It's very good... and one of the better games I've played in a while. But I still wouldn't call it a best just yet. Then again, take it with a grain of salt, I'm still at the beach part.
FWIW, while the story isn't as good and the characters are nowhere near as memorable, most of the AC2 games had much better puzzles.