I know this was intended for Noipoi, but I'm going to answer seriously(for once)
In terms of story, I honestly love how the Genocide path reveals the heroics of the characters(Undyne and Sans in particular)
Main problem with Genocide is how alot of characters just appear(and then just die)or just never show up at all(Alphys and Sans in particular, although Sans makes a bit of sense considering how he acts if you kill Papyrus, and Alphys is implied to have evacuated all the remaining monsters)
But if you just want a happy ending, Pacifist is kinda cool.
I really don't like the fact that Pacifist doesn't really have any like "silver-lining" moments(as in, every choice in Pacifist is always good, with no regard to the possible bad consequences of not killing some of the really evil monsters, which Undertale doesn't really have any, so it's kinda fair. *deltarune does thou,