Hot take:
Pikachu's goodbye is sadder then bye bye butterfree, in fact I don't think bye bye butterfree is actually all that sad.
I just dont think I got as attached to butterfree, it wasn't in nearly as many episodes like Pikachu was. And i've always liked looking at the backgrounds of the episodes cuz it's where you can see the small little interactions and the development. Like in the primeape episode you can see Pikachu start to understand why the hat is so important to Ash when Brock mentions that a hat is like a best friend. Or you see small interactions between Ash and Pikachu in the background and you can watch the two develop from episode to episode. Pikachu may not speak, but you can practically hear Pikachu thinking that it'll give this trainer a chance when it attacks those spearow. Lt. Surge and Sabrina the third time too where Ash and Pikachu battle together and you can get the idea where these two finally start to understand each other through battling. You don't really get that with butterfree. Sure you've got the caterpie episode, the metapod episode, and the shipwreck episode. But not much else. And I just didn't get very attached to butterfree. You've got 39 episodes to get attached to Pikachu at this point, but 5 where butterfree appears, including its goodbye episode and 1 where it's literally just brought out for a battle. Since Pikachu is never in its pokeball you've got so many more chances to see those small interactions and get a feel for Pikachu. And since it's one of the main protagonists and a mute protagonist (besides the pika-pika) Pikachu has to be out of its pokeball to get that development and make the audience care. Butterfree doesn't get that and I never really cared for the goodbye episode as a result.
But pilachu's goodbye, which gets the butterfree montage but actually has more stuff in it, that episode gets me hard.
