Straight from the Firefly, who may overrate the film Serenity but he sure can whip up a poll question. There are a bunch of other candidates I can think of but I decided to limit it to his original five. And I like how he suggested Actor (rather than supporting) because otherwise Cuba Gooding Jr. would be the obvious answer.

Did nobody listen when I said replace Roberto Benigni?

You go from something that's beloved, even if for a short time, and then you make Pinocchio with your 50 year-old creepy self as Pinocchio! It's not a contest!

F. Murray is more of an ensemble man who at the least still squeezed out some worth.
Forrest Whitaker has had the same career after his win as he did before.
Jaime Foxx just got lucky.
Adrien Brody....he may be in second place.

I don't think Benigni is necessarily obvious because I don't give him any credit for his Oscar. He was terrible in that awful film, and he was terrible since. So he certainly didn't squander his potential.

I'm saying F Murray Abraham, because it seems that he soon entered the R. Lee Ermey "Will appear at a postage stamp ceremony if he's getting paid" level of career sabotage.

PS I notice you used may. Good thing to leave yourself that uncertainty

I'm going with Forest Whitaker, mainly because after watching the fairly rubbish Repo Men, I came to the realization that he's been playing the same shlubby, slightly goofy idiot in every film he's been in post-Last King of Scotland.

The difference, at least from my perspective, between Whitaker and some of the others on this list is that he actually had a sizable and notable career before his Oscar win. Jamie Foxx before Collateral and Ray was more well-known for his television work, and his career post-Ray hasn't been much of a dropoff from the films he was appearing in before. I suppose it can be argued that Roberto Benigni had a healthy career in Italian cinema, but most people, including myself, just know him from his two or three memorable roles and nothing else. Adrian Brody has played it smart by not even attempting to outdo his work in The Pianist. Instead, he's chosen interesting but offbeat projects, going into action mode in King Kong while also appearing in more independent and quirky productions like The Brothers Bloom, The Darjeeling Limited, and Splice.

I suppose F. Murray Abraham is probably the most accurate choice here, but I've always seen him more as a supporting player than a leading man. He certainly made the most of his brief moment in the spotlight in Amadeus though.

I really don't think Brody deserves to be on the list given that he's at least tried interesting projects since his win.

And yeah, I think Roberto is the obvious choice.