Pesonally, my fave episode was "Stimpy's Invention", with the Happy Happy Joy Joy song. As much as I enjoyed the early episodes, it really was a violent, gross cartoon. I would never let my kids watch it. I don't think Nick knew what they were getting in to...
On another note, the first time I watched SpongeBob, I saw some similarities between the two shows. Stimpy could have been a SpongeBob...playful, simple and loving. And of course Ren could have been Squidward. Angry, short-tempered and easily annoyed by Stimpy. Ren's love for $$ echoes Mr. Krabs'. There were even similarities in the style, like the painted extreme close-ups (R&S's gross, SB's sometimes a bit gross).
Oh well. I'll take the Sponge any day.