Runners-up: Beetle Bailey, Curtis, Dilbert, Mother Goose and Grimm, Rhymes with Orange, Speed Bump
Candorville is an under appreciated strip I think. Darrin Bell has created main characters with interesting relationships and unique personalities. He handles topical strips better than anyone, able to make a point without sacrificing humor, unlike most political strips. The art matches up with all but the best strips (Get Fuzzy, Lio and Watch Your Head are better, a few others might be just as good). Candorville should maybe be a top five strip.
Runners-up: Garfield (three best runners-up in four days, Jim Davis is on quite a roll), Get Fuzzy, Pearls Before Swine, Prickly City, Single and Looking