I'm surprised I've never written my thoughts on this episode...
I cried SO violently when I first saw the rock heading toward Bulbasaur. I was terrified it was the end.
But really, this was the best possible farewell episode for the best Pokemon Ash has ever owned. His oldest partner besides Pikachu, I think there was a reason he lasted so far into Johto. Ash was genuinely crestfallen at the prospect of leaving Bulbasaur at Oak's. I think there was a lot of love there that wasn't there for many of his later Pokemon in the same intensity.
This episode is basically a love letter to Bulbasaur, and I adore it.