Being a very sheltered child, I can say that this is almost impossible for me! XD
I've watched alot, A LOT of cartoons in my time both old and new, (I stayed up late to watch the 80s stuff as well like Ulysees 31, Mask, Jayce and the Wheeled Warriors, He-Man ect.).
Loved Transformers (and Beast Wars, quite underrated that one but it is definately worth watching).
I think the only cartoons I didn't watch so much were the old Disney cartoons, Thundercats and GI Joe.
I can watch some Thundercats if I want to though. My little brother has some of the DVDs (first season I believe).
Hmmm... Maybe I will after I catch up on Ulysses 31! XD
(Now Ulysses 31 is an awesome show. Infact anyone watched the Dungeons and Dragons cartoon? Man, that was pretty cool and bleak at the same time as well.

)
EDIT: Ah you guys are missing some other cool ones!
Biker Mice from Mars
Street Sharks (If you watched this then you will know why I'm laughing XD)
The Real Ghost Busters
The 90s Marvel cartoons! (Iron Man, The Incredible Hulk, X-Men, Spider-man, Silver Surfer, and The Fantastic Four)
Rocco's Modern Life (Almost as good as Ren and Stimpy (one of my favourites for sure! XD))
Oh, and Teenage Mutant Ninja Turtes (Hero over here in the UK! XD)
EDIT 2: ONE MORE THING! I loved Jackie Chan Adventures too! XD
EDIT 3: Heh. The Mask cartoon. I remember that one, and Ace Ventura too! XD