You know what the best form of immersion is, a compelling story, and characters that make me care about them. The movies that I love have filled that role without the use of fancy 3D cameras, and giant blue cats.
If you were even to look at films in the same genre, 2001 : a space odyssey would be a perfect example. It used special effects to convey a sense of futurism, and to keep you locked in the world Kubrick created, but they weren't the center piece, the center piece was always the story (as an aside, I think the effects of 2001 still look more photo real than avatar).
As always my 0.02 dollars.