Not since the last SNL sketch-turned movie has a stupider concept been extended this far beyond its means. Not funny for 30 seconds? Then it's sure to be hilarious for 30 minutes! 
This is very subjective, because I can't get enough of the Caveman commercials. They just strike every chord with me. Comparing them to a drawn-out SNL sketch is unfair, IMO. Now, the Geico Gecko or "real customer" commercials are crap, and I can't stand 'em.
Go figure.
Huh. I like the gecko and real customer ads, especially the one with Burt Bacharach. But then again, I rarely watch TV and have really only heard them on the radio, which I don't have on all that much either. I could see where the gecko could get annoying, though.
Regardless, I just can't see a sitcom about cavemen succeeding, but if they can squeeze some decent jokes out the premise, I wish them luck. My prediction? Geico Cavemen: The Complete Series (13 episodes, including 5 never-before seen!) will be available on DVD for $15.99 in the near future.