I love the fact that where other shows have a main character as a jerk, Gumball gets called out on his behavior and even feels bad for it sometimes. Seems that he's deep down a troubled individual, at least that's what "The Society" revealed.
Also, it seems Gumball can be very genre savvy when the script calls for it. I find that refreshing, especially in "The Sweaters" where he calls out every single sports movie (and anime) trope before it happens. And to think, the characters in that episode were almost abstract animal types instead of the brilliant 1980's Japanese outsourced to look American but not quite designs. They really hammered that sports anime cliche gag home.
I also find the touch that, despite not having a job or anything, Richard always wears a tie because it gives him a sense of purpose quite nice. Clearly he's the same goofy dad figure invoked by Homer Simpson and Peter Griffin, but with a level of self awareness. It feels like deep down, he is a bit sensitive that he's a goofy character and a screw up. And Nichole rarely takes advantage of the fact she's the breadwinner of the house and Richard is the stay at home parent. She never vilifies him for it, and gets angry and defensive when anyone else does. There's some really nice touches to these characters that give them a depth beyond most animated sitcom families. I'd say the Watersons and the Belchers are my favorite animated families.