Who would you cast in a remake?

No remake.

If there was one, it should be Brad Pitt & Jennifer Aniston.

That would be interesting.

I would counter this question with, "Why does every harmless, thoughtless IMDB conversation attract flamers who just can't leave well enough alone?"

"I drank what?!?"

-Socrates

I agree with the other posters who feel that a remake for this movie is unnecessary and would most probably not surpass the original.

Some of these choices I really disagree with. I mean, Goldie Hawn as Corie's mother - no way! I think Dana Ivey would do a good job (she looks quite like Mildred Natwick)
Corie - Amy Adams! (look at that scene in Enchanted when she is trying to be "angry" - she has that funny and silly wit that is needed) - I could also maybe imagine Kate Hudson in this role if it was set modern
Paul - maybe Mark Ruffalo, even though some people are sick of him
Mr Velascoe - David Suchet possibly

Redford has loads of character in his face while Pitt mostly comes off as a poseur. The only two films where he pulled of some enigmatic brand of "cool" was Ocean's Eleven & "Jesse James". Pitt has a rosebud mouth (which he let hang loosely for years), a cute little-girl nose. Redford's character comes from an almost hawkish nose, a much tougher chin, and a very firm-lipped mouth. To say nothing of the eyes - same colour and shape, but Redford's are far more steely, exression-wise. Pitt's is like a Barbie. Also, Redford comes off as more literate & naturally sophisticated. I think it's do with speech patterns and the diction of that time. So much crisper. Spygame really showed up Pitt's deficiencies in the comparison game, even though Redford was so much older and wrinkled by then.