Inception

I'm not a movie expert, I'm not the guy that knows every great director and has watched every single movie by them. I did watch The Dark Knight and thought it was great. However, it was Memento that I thought was mind blowing :D One of the greatest movies ever.
And how good is Inception?! It's a brilliant film that is extremely well built, making sure you don't get lost in a plot that is not easy! Leonardo di Caprio surprised me on Shutter Island, and now he just delivers another great role. Joseph Gordon-Levitt is even better than Di Caprio (BTW GO WATCH "500 Days of Summer" IF YOU HAVEN'T).
I won't talk about the story, that's one of the strongest points in the movie. I'll just say that it ranks very high on my personal list of movies that gave me that WOW feeling after watching them.
In conclusion, many will say it's great just because it's fashionable to say so. I'll say it's great because I really enjoyed it. Oscar material here hopefully!