The shows I loved growing up were Rugrats, Hey Arnold, Ren and Stimpy, Rocko, Angry Beavers, Spongebob, and sometimes CatDog. I remember watching shows like Doug, Wild Thornberries, and Rocket Power, but I wasn't as big a fan of them.
A few shows I didn't actually watch until I was in my 20s. Avatar (+Korra) and Invader Zim were great. I've also gone through MLAATR and Danny Phantom, which were pretty good.