In order of preference:
Superman - absolutely perfect. Holding back Superman for almost an hour so we cred about the characters was a move that has been often copied, but never bettered. To me, this film really kickstarted the genr of surerhero films.
Superman 2 - what's better than Superman on his own? Superman facing off with 3 kryptonians in the crowded streets of Metropolis. The 'memory loss kiss' was pretty ridiculous, but that was the originally intended ending.
Batman Begins - took a franchise that had been pretty much killed off and resurrected it with style and class. Even my mum loves it, and she generally refuses to even entertain the notion of superhero movies because she finRAB the notion 'ridiculous'. Plus, by using Scarecrow and Rha's Al Ghul as the villains, the casual audience focused on the struggles of Batman/Bryce Wayne. Also tapped into the psychological crises of a Superhero in a way I don't recall seeing before.
Batman (1989) - would have been higher had Begins/The Dark Knight never been released. Typical Tim Burton kookiness, outstanding score from Danny Elfman. Great casting, even if Batman is overshadowed by Jack Nicholson as Joker.
Iron Man - A big, bright, bolt of fun. Downey Jr. is perfect.
Blade - Wesley Snipes. Big Sword. Cool. Seriously though, of all superhero films, this feels most in the 'real' world. Dorf is also excellent as Deacon Frost. Although considered better by many, I just didn't like Blade 2 as much, and lets not mention Blade Trinity, deal?
X-Men 2 - How do you take a good origin story film and make it better? This is how. From the White House opening, to Jean's sacrifice and the hint of her resurrection (including Famke's closing voiceover and the brief hint of a phoenix shape on the water), this film never lets up, and even the quieter moments develop the characters further. I'd love to see what Singer would have done with X-Men 3
Superman Returns - For being a faithful update of the much loved original. Spacey and Routh are excellent, Bosworth i thought was ok. The kid I could have done without, but I don't think of him when I think of the film. For me, the scenes of Superman being Superman and saving Metropois, lifting the Kryptonite island, and the plane rescue, Those three scenes are reason enough to give Singer another crack at the character.
Batman Returns - Why this and not The Dark Knigt? Because, and I love TDK, this film is, to me, a better sequel, and relates back to Batman (1989) the way Superman 2 does to Superman. TDK is more it's own movie. The star of this film is Pfeiffer as Catwoman/Selina, oozing psychotic maniac in every scene she's in yet remaining totally alluring.
Spiderman 2 - for the train top scene. Nuff said. And for being the peak of the series before the third film succumbed to the 'too many villains' trap.