Can't go past Breaking Bad at the moment. In terms of comedy I think It's Always Sunny in Philadelphia is a classic, but you have to watch it from the beginning and persevere through a relatively slow season and a bit until Danny De Vito comes in. I don't think I've ever laughed as hard as I have during that show.
I also find The Office to still be quite good, despite Steve Carrell's departure. Can't see it going for too much longer though.
Anyone seen previews for the new series Alcatraz? I can't decide whether it'll be Lost 2.0, or something that actually makes sense...