I don't think Follies has a broad enough appeal outside the theatre community to be a successful film at all. Even the theatre community is divided on it.
Personally, it's far from my favorite Sondheim show, but in saying that, I'm referring primarily to the subject matter and the "book."
It's way too maudlin, self-aware, self-pitying, dated, and theatrical. The songs, as stand-alone pieces are little gems... but the parts, in this case, are far greater than the whole. I think it would be a dreadfully boring film.
But I could see Bill Condon's idea of adapting Ted Chapin's book "Everything Was Possible" much more than adapting the show itself.
As far as Company, I don't think the dated, bossa-nova and '60s-style score would play well in a film today. The Ladies Who Lunch would come off as an overwrought, Ultra-Lounge meltdown. The sentiments toward couples, relationships, pot, alcohol and the sexes in general would also seem like a "very special episode" of That Girl. The impact would be lost or trivialized for 9/10 of the film.
Into the Woods and Sunday In the Park, have enough of an eclectic "timeless" sound to the music that each could be adapted for film with much greater success. Plus the emotional ideas and themes that each explores are timeless as well.
"Jaws is the Citizen Kane of movies."
blocked: logan2, Diamonds3, Hamilton22