Using imdb's Bayesian scores:
10) The Departed, 2006. Factors: Star-studded cast with DiCaprio, Damon, Nicholson, and the elder Sheen combining to star in 7 other top 250 movies, plus Scorsese has directed 4; stole its plot from Infernal Affairs, another top 250 movie; some hilarious scenes, especially ones including Walberg and Baldwin; legitimate plot twists. Ratings-wise does well across the board and picks up the female vote. Have to assume that the love story angle helped it there.
9) Amélie, 2001. Factors: Very cute and romantic, with the rare female protagonist; French so more explicit than you might expect; flat out dominates the female vote, especially 18-29, but doesn't get betrayed by the male vote like Beauty and the Beast does.
8) Wall-E, 2008. Factors: Fits well into current technophobic apocalyptic dogma; sweet beginning with no dialogue; "fun for the whole family"; refreshingly short. Surprisingly, rated rather poorly by those aged 45+, especially females, who give it a measly 6.1.
7) LotR: Two Towers, 2002. Factors: Best fight scene of the decade in the last scene, with Legolas pulling off the coolest moves. Not surprising that males under 18 give this one the highest rating.
6) Memento, 2000. Factors: Sick topsy-turvy plot; eminently rewatchable; Chris Nolan directed (he kills it on imdb); confusing for non-movie watchers making it an "insiders club"; street cred for having a solid psychological basis (see patient HM, who also learned to do mirror writing); and great ending.
5) Avatar, 2009. Factors: Innovative 3D presentation; fits well within current environmental dogma; James Cameron directed (he quasi kills it on imdb as the director of 2 top 250 movies). This is a controversial pick as the rating is inflated because it just came out and the score will probably fall quite a bit. Wasn't sure what to do so it remains here for now.
4) LotR: Fellowship of the Ring, 2001. Factors: Best visuals of the trilogy and a rather scary scene when the hobbits first hide from the dark horses. Does quite well with females considering it's so action oriented--females 18-29 give it the highest ratings of any cohort.
3) City of God, 2002. Factors: Lots of violence and a long winding story with a sympathetic narrator. This movie went viral--countless people listed it as their favorite movie for a while in the mid-2000s. Of course the conformity theory makes no exceptions and now the public has generally cooled on it. But, the respect remains.
2) LotR: Return of the King, 2003. Factors: Visually impressive, plus a huge nerd following. Could have easily dissapointed (see Star Wars VI) but did not. Very polarizing, though, with 5.2% ratings of 1.
1) The Dark Knight, 2008. Factors: Heath Ledger's posthumous performance guarantees goosebumps; Chris Nolan directed (see #6); Batman Begins was top 100 so it has a strong pedigree, Christian Bale starring (he's in two other top 250 movies); and round two of a trilogy so execs OK'd the ambiguous ending. The perfect storm. Did not drop as much in score post-DVD as I thought it would, with demonstrated staying power into the next decade.