While I certainly don't think Avatar divides the cinematic world into Pre-Avatar and Post-Avatar as some people seem to think, it is an exceptionally entertaining piece of cinema delivered by a phenomenal director at the top of his game.  It's big, it's loud, it's gorgeous, and more importantly there is a well told albeit predictable story at its heart.  Pandora is without a doubt the star of the show and Cameron succeeds in transporting you there completely for a three hour tour of all the wonders it has to offer.  The sense of wonder and exploration conveyed by Sully along the way is completely believable since you kinda feel the same thing yourself.  It is by no means the best movie ever made, it isn't even the best movie to come out this year, but it is the perfect summer event film (which just so happened to be delivered in the middle of winter) that succeeds where so many big movies have failed in recent years (I'm looking at you Star Wars Prequels, Indy 4, Transformers 2, etc.).  This movie is a showcase for everything the theater experience still has to offer and I highly recommend you see it in 3D and on the big screen.