I liked SSE, though I do think it could've been executed a lot better. Also, maybe integrate more elements from the various Nintendo series as opposed to these random creatures.
But I liked it.
Melee's adventure mode was boring (sorry for not being a Melee fangirl), and had even less substance. As far as I'm concerned, it was just a random adventure that meant nothing, one which you could do with every character. I liked the 'story' that SSE had, and I definitely wish there was something like it in SSB4, but polished up a bit.
HOWEVER. If taking out an SSE-style mode means more characters/stages, improved gameplay, and an earlier release date, then I'm all for it. For me, Smash Bros is still primarily about the VS mode.