One of the cool things about Inception is that you don't even need to rewatch the movie to think about how cool some of the ideas behind it are. Just thinking about the implications behind some of the stuff in there is already epicly huge (is anything real? Are the 'reality' parts dreams too? If it is all a dream, who's is it? And if it's not, what happened to Cobb? Is anyone even real?).
But my favorite part is easily when Mal looks over at Ariadne, even when you know it's coming, it's scary as hell. It's not even like she whips her head over or anything, she does it at a normal pace, but the glare punctuated by the score at that time is more terrifying than any modern horror film.
1st viewing - 'THIS IS MAGIC.'
2nd viewing - 'TOM HARDY IS BRILLIANT.'
3rd viewing - 'Nolan is a genius, this is actually one of the best films I've ever seen'
4th viewing - 'Not quite as good now that I've figured it all out'
5th viewing onwards - 'One of the most stylish, atmospheric and brilliant rides ever. Thank you Nolan. This is actually one of the best films I've ever seen'
Actually for me it kept getting better the more times I saw it.
1st: Baffled, confused, and somewhat disappointed
2nd: One of the best movie experiences of my life. ahhhmazing, and made much more sense
subsequent viewings: love it love it love it. Keep finding new little things in it