Comedy RPG done right? I think that works best when it's an RPG first, and funny second. For example, the first two Paper Mario games. I laughed at those a lot more than I laugh at most of these so-called comedy games, but if someone asked me what kind of game either one is, I wouldn't say a comedy, I'd say a JRPG.
What makes the Portal series so good is the variety in the crew that made it. It didn't have game designers trying to write comedy that they didn't know how to write, nor did it have comedians writing the game strictly for humor's sake and shoehorning the game around it. Rather, it was game first, designed and programmed by game folk, with a story and humor carefully woven in by people who are good at that.
People have specialties. You wouldn't hire a sound expert to do the lighting in a movie, you wouldn't cast a cameraman in the lead role simply because he showed up, so why do game studios keep trying this? Leave the game mechanics to game designers, and the comedy to comedians. Have the two teams work together, but don't try to use one as a replacement for the other. If someone is good at both, that's fine, but don't try to force it.
P.S. Thanks