1) The Dark Knight - even apart from Heath Ledger, the incredible cinematography, action and music, this is my top Nolan film (and favourite film of all time) because of the sheer power of the plot and story - I've never seen a film so perfectly written, blindingly faced-paced and packed with twists and turning points, and yet never confusing or overloaded. The atmosphere and immersive feeling I get watching this film has also never been equalled by anything else. The first time I saw it, my enthusiastic cousin was up for re-watching it immediately the moment we finished, but I just went straight to bed and lay there all night in torment, playing it back in my head. I've never been so affected by a piece of cinema.
2) Inception - again, a very immersive experience, and the editing at the climax really, really impressed me. Another great script, although in my opinion the performances don't quite equal the ones in TDK.
3) Memento - I just love the cleverness of the premise and the conceit of having it play backwards. It's just such an amazing experience sitting there watching it for the first time, and instead of not knowing what's going to happen next, not knowing what has already happened. So original, and so well done. Admittedly, it doesn't have the same spectacle of the later films, but it's one of my all-time favourites.
4) Batman Begins - I feel the writing isn't as good as TDK (the ending is a bit too Hollywood, and the Microwave transmitter just makes me cringe), but otherwise a very entertaining and nicely dark story, and I really like Tom Wilkinson's and Cillian Murphy's performances, in particular.
5) The Prestige - Hmmn, it feels somehow wrong putting it 5th because it's such a great film. I really, really enjoy the whole period-drama element of it, and the magicians aspect, and the labyrinthine plot and multiple twists are very enjoyable. Just not as awesomely original and epic as the previous four, I think.
6) Following - staggeringly impressive when you think of the budget and other constraints, and I love the music, story, and use of locations and props, but of course it does suffer from being too short and perhaps not quite as refined and well-honed as the rest.
7) Insomnia - like The Prestige, it feels strange giving such a solidly excellent film last place, but that's all it really is; a solidly excellent film. There really is little special about it, apart from perhaps Robin William's performance and some of the cinematography.