Stand up comics/comedians are good at delivering punchlines, but not very proficient as it relates to improvisational acting. Guys like Jonah Hill, Seth Rogan, Paul Rudd, Tina Fey, Will Farrell and Steve Carel to name a few are all trained at improv (Second City Impov) and writing full fledged scripts and/or sketches, their movies tend to have more realism, as opposed to over the top physical gestures like Carrey is well known for. I rather watch a Judd Apatow movie over a Jim Carrey movie, at least that's more my taste.