I'd say Ulrich's dad from Code Lyoko... but from the two episodes he appeared in... I'm not terribly sure.
Don Wei in Oban Star-Racers is pretty intelligent, just a bit too harsh. Sure, he had his "dumb" moments, but overall, he wasn't a "dumb dad" character. Then again, this is a more serious series, and not comedic like The Simpsons or Fairly OddParents.
Dexter's Dad from Dexter's Laboratory didn't seem all that stupid, just a tad immature at times.