Hm... hard to say, since I like so many, including the following:
Pokemon (the oldschool stuff), Digimon, Ben 10, Angry Beavers, Swat Kats, Danny Phantom, Invader Zim, Megas XLR, Freakazoid, Histeria, Animaniacs, The Grim Adventures of Billy and Mandy, Spongebob Squarepants, Batman Beyond, Avatar: The Last Airbender, Kim Possible, Super Robot Monkey Team Hyper Force Go, Batman: The Brave and the Bold, Pinky and the Brain, Tiny Toon Adventures, Looney Tunes, Tom and Jerry Phineas and Ferb, Ed Edd & Eddy, Fairly Oddparents, Teenage Mutant Ninja Turtles, Codename: Kids Next Door...
The list goes on and on. Unfortunetly, most of the show I like have been taken off the air and are replaced by, well, crap. Especially the non-animated tweenie stuff that TV stations seem to LOVE now...