As soon as I posted that, I realized that people would ask for my reasoning, and it would probably not be appreciated. LOL.
Anyway, there are a lot of different skills and talents that are required to be a good actor, but the degree to which you need certain *specific* skills differs between the stage and screen. My personal opinion (and I know some will disagree) is that MF is a great physical actor and good with the microexpressions that register on screen, but his vocal instrument and range is really not his strong suit (he's even occasionally monotone), and that's maybe the most important factor to a stage actor. I know he acted in a few plays, and even got some good reviews for a short stint at the Edinburgh Fringe Festival (or something like that), but I think it's somewhat telling that he didn't get any real *breaks* from a stage career, which is far more typical in the UK/London.
I remember when he did that stage live-read of The Big Lebowski, and the subtext of a few of the formal reviews, and the overt comments of people on Twitter was that he was kind of embarrassingly bad.
And I'm not trying to be insulting here. There are plenty of superb screen actors whose talents do not translate to the stage. Julianne Moore and Jessica Chastain are two of them.