Yes, this is a classic. I watch this film at least every other year, and Fincher is one of if not my favorite working filmmaker today.
Should this make it in the Canon, it would be great to have this paired against Zodiac; I believe the latter is my favorite of the two, but that would make one heckuva matchup.
Oh, and to Amy's point about Fincher not caring about characters or character development in Se7en, see Roger Ebert's Great Movie review of this film, in which he rightly argues that this is a character study disguised as a serial killer thriller.
