As a kid, I found comic strips funny (chiefly Calvin and Hobbes and Far Side), but their humor is much too one dimensional and dated for me now, just as sitcoms are as well. They're much too formulaic and mass produced, lacking the creativity of what I enjoy now.
That being said, comics certainly are comic. They just don't take comedy very far. Granted, the same could be said about crappy email forwards, but they're at least a bit better than those.