I think Mel Smith is possibly one of the funniest people on earth. Griff Rhys Jones is, however, the opposite. He's funny, but not in a comedy sort of way. I can't really describe how un-funny I find him, aside to us the comparison that he reminds me of an anti-Mel.
Now oddly, Alas Smith and Jones was an incredibly funny sketch show featuring Mel and Griff as a variety of characters in amusing situations.
One consistent piece that appeared in ever episode, was a conversation between Mel and Griff, in which only the profiles of their heads were seen and they'd discuss a random topic.
The show was 30 mins long and ran for years.