Can't argue with "Somewhere Over the Rainbow", although it's not one of my personal faves.
From the Sound of Music, I personally would go more for (my misspelling of) "Eidel Veiss" or whatever it is, or for "Must Have Done Something Good". But that's just me. My wife would likely argue for either "How do You Solve a Problem Like Maria" or "Climb Every Mountain".
From Singin', I'd probably go for Make 'Em Laugh, but that's just 'cause I'm a sucker for the comedy guy. The comedy guy always has the harder job in those things. I liked Danny Kaye better in White Christmas, too, although he doesn't have a song that really blows any doors off.
Wish to heaven I could remember any of the songs from Cover Girl, but that probably means they weren't that memorable.
Again, personally, I'd differentiate between "Songs that were made specifically for a movie" and "Songs that were made for a stage musical and later got brought to the movie version of that musical". But my musical-fu is not strong enough to definitively say which movie musicals were from stage musicals. I know that Sound of Music was, of course. But otherwise, I find myself putting in a lot of songs from stage shows that got made into musicals. Stuff from West Side Story, for example, or My Fair Lady.
And staying with songs done on-screen (as opposed to score music, in which case I'd be adding in "Who Wants to Live Forever" from the Highlander soundtrack, released stealthily in the U.S. as the A Kind of Magic Album), though, I think there are some newer songs that deserve credit. I loved the montage song from South Park ("Tomorrow Night", I believe?), and several songs from Jack Black's School of Rock were just wonderful. Was every song in The Commitments a cover of an older song, or were some of them original? The female solo where she looks at the crowd with smoldering eyes and belts out the "I have never, Never, NEVER... loved a man... the way that I... love you," ought to be in there somewhere... although that could just be me. I have weaknesses for that type of song (and, er, that type of singer -- although I had the darndest time convincing my wife, a coloratura soprano, that dropping to a smokey alto voice was really really okay with me when she was singing personal numbers).
Although admittedly, that's moving into broader definitions of "musical" and away from the classic musical form
