The Dark Knight
Sequel to Batman Begins, with Heath Ledger's definitive take on the Joker (as inspired by Tom Waits). The movie inspired an epic 12 means 12 rant from Mark about parents using the film as a babysitting service. (Mark Lawson put the other side in the Guardian).
Mark was also annoyed that other critics kept referring to The Dark Knight as a crime movie in order to avoid saying it was based on a comic book.
Regarding the content of the movie itself, Mark felt it was somewhat problematic - especially the sequence with the boats, which was a real case of author's message for the hard-of-thinking. The amount of money it made would allow director Christopher Nolan to go on and make Inception, however, so that's alright then.
Mark also felt it was too long. When queried by a listener, who rhetorically said "Is The Godfather too long? Is Apocalypse Now too long?" Mark replied, "Ask me this: is The Deer Hunter too long?" Simon Mayo pointed out that that was not what the email asked. Listener Rob in Esher helpfully did then ask, and Mark replied, "Let me tell you how too long The Deer Hunter is: about three hours."
Overall, out of that summer's blockbusters, Mark actually preferred Hellboy 2 to this.
The fact that it was a drop from Batman Begins and that Mark preferred this film's sequel, The Dark Knight Rises, suggests that Nolan's Batman films follow the High School Musical rule.