I think TV currently does a good job with this. Comedy should be 30 mins and drama a hour. The only changes I would make, is upping Californication and Weeds from 30 mins to the full hour. The rest is fine how it is.
Well, I like my drama shows to be an hour, like "Life on Mars", "Blackpool" or "Ashes to Ashes". Sitcoms, and comedies in general, I prefer to be half an hour long. Although I still love Only Fools and Horses, and their episodes went to 50 minutes long for series' 6 and 7.