I just don't think there are enough movies and roles worthy of such a fine actor in this day and age. It makes me think of Eddie Murphy. Some of his first roles ("48 Hrs.", "Beverly Hills Cop", "Trading Places", and "Coming to America") were so perfectly suited to his talents, but it was all pretty much all downhill from there (with a few exceptions).
People often say he just made bad career choices, but I can't think of a lot of movies that came out in the 30 or so years since his first big role that he could have shined in.
Murphy has traditionally had a lot of input for shaping his movies and the parts he plays in them. For example, he was a writer and/or producer on some of his worst movies, including:
- Norbit
- The Klumps
- Vampire in Brooklyn
- Boomerang
You also have
this interview with John Landis who, for what it's worth, describes how Murphy had changed by the time he made "Beverly Hills Cop 3" from a brilliant comedian into a prima donna:
TRADING PLACES and COMING TO AMERICA, he was very direct-able. On TRADING PLACES, he was fantastic. He was very young. It was his second movie, and he was full of enthusiasm and he was happy. He was a pleasure and a joy...He always took direction from me. He was great. On BEVERLY HILLS COP III, it was bizarre, because he didn’t want to be funny, and there was nothing I could do to make him funny. I actually learned later that he was very jealous of Wesley Snipes and Denzel Washington and Sam Jackson, all of these guys who are making these big action pictures.
I actually gave him a gag, and he said to me, “John, Axel would be a wiseass if he did that.” I said, “Eddie, Axel is a wiseass.” He says, “No, he’s a man now.” I thought, “Uh oh.” If you look at that movie, it’s like, “Come on Eddie, be funny,” and he’s not. He’s a very interesting guy. He’s really quite gifted with extraordinary talents, but now you only really see it when he’s in disguise.
Therefore, I think he deserves a lot of responsibility for his more recent movies being bad.
As for what movies he could have been in instead, well, he was nominated for an Oscar for Dreamgirls. However, instead of following that up with more "prestige" work, he made Norbit.
You also have to consider how many movies that were hits for other people he could have starred in.
Finally, given his success in the past with sketch comedy, if he had wanted to, I think he could have even done something like Chappelle's Show.
Marilyn Monroe, on the other hand, is someone I think should have had better roles and might have if she'd been born/started acting later or lived longer.
If she had lived longer she might have aged more into the kind of stuff that Liz Taylor was able to do. But if she had been born later I think she would have probably never made it big. In the 1960s and 70s, "full figured" women and comediennes were not in great demand. I think Monroe would have been too different from the blonde California athletic types that were all the rage by then.