Robert Preston played an openly gay character in Victor/Victoria but is usually remembered as the straight Prof. Hill in The Music Man.
I really hope I’m missing something.
How about Patrick Stewart as the delightfully fussy old Sterling in JEFFREY?
Laurence Olivier played gay in Spartacus and straight in The Entertainer.
Hume Cronyn played gay in There Was A Crooked Man and straight in pretty much anything else, like Cocoon.
Russel Crowe played a gay man in The Sum of Us (pretty good, btw), and a straight man in L.A. Confidential, Proof of Life and most of his other recent movies.
Hugo Weaving’s roles as Agent Smith and Elrond were pretty asexual, but he does play a gay man (or a drag queen, at least) in The Adventures of Priscilla, Queen of the Desert
Otto…
What makes you say Roy Schnieder played a gay man in Marathon Man? I must have missed something there.
If you believe Gore Vidal, Charlton Heston played a bisexual man in Ben-Hur…
And Tony Curtis in Spartacus
I’m not sure how it plays out in Goldman’s book, which I keep meaning to read but never have. But in the movie it is strongly hinted that Scheider and his boss are an item.
- Tamerlane
Actually, all three of the main characters in that movie - Guy Pearce, Hugo Weaving, and Terence Stamp - are straight. When I saw the movie, I thought for sure that not only were they gay, but wondered if Guy and Hugo really were drag queens in Sidney (this was before either of them were very well known actors). Their acting was incredible.
Terence Stamp has been in too many movies to list (check IMDB.com), and Hugo Weaving has since gone on to play Mr. Smith in the Matrix, and Elrod in LoTR, among other “straight” parts. (that is, if you can consider playing the King of the Elves a “straight” part!)
IIRC, Michael Caine and Christopher Reeves played lovers, a bisexual and a homosexual respectively, Death Trap.
Anthony Hopkins played a gay Richard the Lionhearted in The Lion in Winter.
I’m wondering - how can you compare differences in vocabulary, pronounciation, etc. if the actor is playing a role? You’d be comparing how the actor chooses to portray a role/character, wouldn’t you? How can you compare two different roles 
The book explicitly states the homosexuality of Scheider’s character.
Billy Crystal played a gay character in Soap…
-Rav
Kathy Bates played a Lesbian in Primary Colors and a straight in Titanic, at about the same time.
Michael McKean played gay in “Best in Show”, but straight in “Spinal Tap”.
Christopher Guest played gay in “Waiting for Guffman” but is married to Jamie Lee Curtis in real life.
Derek Jacobi played gay in Breaking the Code (1996) and Love is the Devil (1998). I don’t know if he’s gay or straight in real life.
Is Anthony Daniels straight? (If not, nevermind)
Jude Law plays Oscar Wilde’s lover in “Wilde”, and a straight snob in “The talented mr Ripley”. (The reason why I mention his straight role in “Mr Ripley” is because I don’t think the two characters he creates in the respective films differ very much.)