10) "The Philadelphia Story"
It's odd to start this list with one of my least favorite Stewart performances in a movie I love. Stewart could play a tough guy, but he doesn't seem like the hard bitten reporter here. He has a couple of good scenes (love the what a gentlemen does speech), but Cary Grant, Katherine Hepburn and even Virginia Weidler (the kid) out shine him. His Oscar for this film that was probably a make-up for "Mr. Smith Goes to Washington".
9) "Winchester '73"
Before Sam Peckinpah, these Westerns that Anthony Mann did with Stewart are what people thought of when they talked about "Adult Westerns". Stewart really is a tough guy in these films. (He was, of course, a tough guy in real life. He was a decorated pilot serving in WW II, and I believe in Korea and Vietnam.)
When I worked on my bad Stewart impression, I went to Elwood P. Dowd and his wonderful speech about how he met his 6 foot rabbit friend.
7) "The Man Who Knew Too Much"
Stewart made four films with Alfred Hitchcock, tying with Cary Grant for the most leading man performances with Hitch. This film is one of those rare remakes that's better than the first. Stewart is very good (though he seems like an old father.)
6) "Mr. Smith Goes to Washington"
The film Stewart should have got an Oscar for this film, especially for the filibuster scene. One of the most patriotic films ever made (and I mean that in a very good way.) Those Republican, Capra and Stewart, worked well together.
"Rope" is the only Hitch/Stewart collaboration that won't make the list (though I like "Rope" very much.) "Vertigo" makes the top ten all time film lists of many critics. It captures the state of a dream, a nightmare.
4) "The Man Who Shot Liberty Valence"
Getting to see John Wayne and Jimmy Stewart work together is a very happy thing. This is the go to film for impressions trying to do either actor. Also, fairly profound meditation on history and legend.
3) "Anatomy of a Murder"
Probably my favorite courtroom drama. Sordid material of rape, handled with in a very mature fashion by Otto Preminger. Stewart's ah shucks country lawyer is smarter than everyone else thinks he is, but not as smart as he thinks he is.
2) "Rear Window"
Not quite my favorite Hitch film (but easily in the top five), but Stewart is great as a photographer stuck in a wheelchair in his apartment. With the limitations of movement, Stewart still delivers a powerful performance. And Grace Kelly is beautiful.
1) "It's a Wonderful Life"
Favorite film ever. 'Nuff said.