Personally, I think the live singing employed for the movie version of Les Miserables worked. It came out raw and that was consistent with the feel of the entire film. And while I think that Anne Hathaway's version of I Dreamed a Dream perfectly encapsulated the suffering depicted in the song, here are some theater version of songs that were just performed better.
Meanwhile, the movie version of Do You Hear the People Sing, Red and Black and of course I Dreamed a Dream can more than hold their own over some of the best versions posted online. All of Russel Crowe's songs, however, can be performed better by just about anyone.