There are some series out there that just jump out at me, I love the character designs so much. Note I haven't actually seen more than one or two of the shows in question (excepting TDI) but I do love their character design and would gladly watch them sitting around playing pinochle.
I just like the way the characters look. Simply designed, you get an idea of what each is like just by looking at them, and the show is consistently funny besides.
Last in my list of cartoons I just like to look at if not neccesarily to watch, is 6teen.