By the time I was allowed to watch TV (when I was very young everything but PBS was typically banned), Saturday morning cartoons had been largely replaced by Friday night/Saturday night cartoons, but I still watched the Saturday morning stuff pretty religiously too, at least on Kids WB (and flipping to Fox Box when bad shows were on). I really liked Jackie Chan Adventures, Xiaolin Showdown, and (sadly) Mucha Lucha. The one I refused to miss was always Pokemon, but I think I was already getting bored of it by 2003 or 2004 because I hardly remember what happened in that series anymore past the Gold and Silver stuff.
Of course, Friday/Saturday night with stuff like Kids' Next Door, Puffy Hi Hi AmiYumi, Teen Titans, Justice League, etc. was way more exciting and I was always much more interested in that.