Hmm ... Vimes in G!G! is hardly a flattering picture. He is bitter, cynical, and often drunk. The best you can say about him is that he is persistent.
Carrot becomes less and less likeable after Feet of Clay (and definitely in TFE). He is redeemed somewhat in TLH, but there he is more or less a supporting character.
Moist is supposed to be nondescript and unmemorable. Having a dime-a-dozen face is the whole secret of his success.
I think women are judged more on their appearance than men in the real world as well as in Discworld. This is unfair, of course, but no-one ever said the world was fair. *shrug*
We also get female characters who
do get described favourably. Take, for instance, Vena the Raven-Haired (TLH), or Herrena the Henna-Haired Harridan (TLF) ... or Eskarina Smith.
Some male characters also get described
unfavourably - for instance, the entire faculty of UU!
They are lazy, greedy, and rather stupid, but still likeable (in an odd way). The only two who are
not lazy or stupid are the Librarian and Ridcully -- and some Archchancellors before Ridcully are also fairly lazy, if not necessary stupid.