The Amazing World of Gumball is a really charming show. It has creative characters and animation, very good writing, and the writers never forget to make the show appealing to the demographic yet make even the oldest of adults laugh at it's comedy. The show is very colorful and have interesting artwork that could rarely leave a child unamused just for a moment. Gumball's parents, Nicole and Richard, are both wacky and funny in their own ways, of the latter being a lazy slob but occasionally entertaining, and the former a hardcore amazon and workaholic who's really strict with her rules, yet kind-hearted deep down.
Darwin's naivete and kindness can be what sets him apart from our self-centered protagonist, and leaves a refreshing breathe of air. Heck, even their little sister Anais, who's usually very serious, can be funny.
While I think the first season episodes will always be classic, I mostly recommend season 2 and onwards. It feels like it was the time where writers felt on ground with how they should make the show and how the jokes and gags shall run. I strongly recommend episodes like "The Bet", "The Job", "The Dream" and "The Watch". And that's only the second season. Recently I watched the first season 3 episodes and it was a really promising debut, so I think it's the rare occasion where seasons will get better and better. Hopefully.
Some may find the witty humor annoying, but I find it immensely amusing and works to keep the viewer entertained until the real punchline kicks in.
I could go on forever, but here's the short version; It's a really cute, funny and charming show that keeps the overall jokes clean with occasional adult jokes slipped in. If there's a cartoon next you want to watch, watch The Amazing World of Gumball.