I think it's tough to say when that particular trend "peaked." Consider:
http://www.youtube.com/watch?v=k3s8sEYzHWQ or http://www.youtube.com/watch?v=Q_TGQ7rGL-Q
Or even:
http://www.youtube.com/watch?v=F1MgjQOR_JA
;)
There's a specific genre, "fat-dumb-slob-married-to-woman-who-always-knows-best", which Family Guy is the pinnacle of (it's an old genre of course, related to the theme of women marrying beneath their status, which has been a major literary device since time immemorial.)
I think this trend probably peaked a few years ago (Family Guy is a good example.) You can actually see it reversing if you watch King of the Hill: the earliest episodes generally show Hank as a small minded redneck, whereas later episodes portray him as a lone voice of sanity.
Anyways, if you look outside of comedies, there are plenty of masculine male leads in popular shows (Jack Bauer comes to mind.) As for race, I can't even think of a popular drama where the male lead is black (and the other characters aren't.) But maybe I just don't watch enough TV.