It always reminds me of Lord Of The Rings. I disliked the first one and when I told people this the first things they said was always "yeah, but have you read the book?" I hadn't, but in my view a text should be able to stand on its own and not rely on its literary counterpart to prop it up.
Likewise with Avatar I've heard people didn't like it and the first question to them was always "yeah, but did you see it in 3D?" Now I know it was designed to be in 3D, so in essence you aren't getting the film as it was intended if you don't see it in 3D. But I think that if a film needs 3D to make it good then you have to question how good it actually is. If the 3D is such an important part of the film then I won't get it on DVD, at least until I can get it at knock down price in a year or two. Why pay £15 for a new film when I could get the Rocky box set for the same price?