In honor of the Academy Awards, here are the ones I've rated as 10 on imdb.com (out of 713 items rated, at last count). In order to rate a 10 with me, a movie needs to change the way I think, forever, and for better.
A few of these are TV; I haven't rated too much TV, though. They are in no particular order.
The President's Analyst ('67 political satire with James Coburn)
The Dead (John Huston's last film)
John Adams (TV miniseries)
Angels in America (TV miniseries)
Man on Wire (documentary on Philippe Petit tightrope walking between the WTC buildings)
Lord of the Rings: The Return of the King (sorry, non-fans: Peter Jackson did it right)
30 Rock (TV; duh)
The Godfather: Part II (Robert DeNiro, talking Italian)
True Grit (not the John Wayne version)
Children of Men
Dr. Strangelove (my all-time #1 favorite, still)
Fantastic Mr. Fox
Being John Malkovich
The Diving Bell and the Butterfly
The Maltese Falcon
Miller's Crossing (my favorite Coen brothers, and that's saying something)
Paths of Glory
Ran (Kurosawa does King Lear)
The Man Who Wasn't There
The Simpsons (TV)
I will be happy to address any omissions you may cite.
For my 2012 picks of favorite movies, see here; and the post and comments to it also have my Oscar picks. Bet upon it!