I'm kind of stickler on this one - Rurouni Kenshin/Samurai X series...
I originally watched this series when I was younger in the Eng-Dub versions that were on TV.
The biggest thing that I have to emphasize about this series, though, is that it HAS to be watched in it's original language (even if you have English subs). Do not use the English dubs. The story behind this series is extremely poetic, which does not come across in the Eng-Dubs. And if you catch the order properly between the plots and the movies, it comes out even better. (Start with Samurai X, Trust & Betrayal).
I watch this series once every couple of months just to remind myself of a few things.
I have watched Rosario-Vampire, which I thought was OK.
I used to love DBZ, but I just can't watch it anymore...
I watch Naruto episodes here and there (TV/Eng-Dubs), but am not in love with it.
Used to watch the Johnny-Quest series, Sailor Moon, etc. (old school, classic/clean Cartoon Network) - never watched Ed, Edd, and Eddy (GROSS). Haven't seen any of them in a while and frankly not that interested at this point.