Sissy Spacek is on another level

Lange, Keaton and most actresses for that matter could not play Babe.

Babe requires a certain type of actress - the child/woman type which Spacek fits into.

Also in many ways, Meg is the most tragic character. My career and life appeared to have spiralled down and Lange is one of the best of portraying this kind character arc.

On the other hand Lange could have played Keaton's role.

Interestingly when finance was first being raised for this film in 1981 (with Jonathan Demme as director) the cast line-up was Diane Keaton as Lenny, Sally Field as Meg & Sissy Spacek as Babe.

By the time the film found funding, changed directors, etc the casting had changed from Field to Lange who was at the time a more sought after actress than Field (despite the fact the Field as won two Best Actress Oscars).

Mind you, Field could have played Meg or Lenny, not sure about Babe in her case.

Also, Beth Henley was most impressed with Spacek. Whilst she never said she thought Spacek was better than Lange or Keaton in the film she did state that Spacek played Babe exactly has she had written the part. I have never read or heard any comment from her on Lange and the only thing she every said about Keaton, which was in 1981 or 1982, was that Keaton was 'too old'. Keep in mind that the characters in the play are in the 20's, however, Keaton, Lange and Spacek were in their late 30's when they filmed the film.

I also think one of the reasons Spacek got most of the acclaim for the film is for a number of reasons. Babe is probably the best role in the film and at the time Spacek wasn't known for comedy, it was her first comic performance, whereas Lange and particularly Keaton were known for doing comedy. Critics were quiet shocked and surprised at the time seeing Spacek play a comic role and pulling it off so effortlessly. Even critics who didn't care for the film tended to praise Spacek's performance. Hell, even the New York Film Critics gave her best actress of the year.