Well, I took a look at the IMDB and figured it out: his career has been one awful movie after another with only the grace of a few standouts and SNL keeping him in the limelight. There's no doubt he can be funny, it's just nowadays he seems to hock himself out to anyone for a paycheck without any thought towards what he wanted to do during his career. Hell,
take a look yourself. The man has more bad movies to his credit then good ones. Maybe if he chose his roles a bit better he would be better off.
Or he could be suffering from the Martin Short curse of fucking themselves over and not realizing that they're starting to suck until it's too late.