Finding 4 is pretty simple for me.

Clannad
Little Busters!
Umineko no Naku Koro ni
and Final Fantasy X-2 HD

Seriously, why is it so difficult to find a group of people that know these storylines? Well, I know why, but it'd still be great if more people got to know them. I even started a Let's Play for Little Busters! right here (see my sig) exactly because I feel they are far too unknown round here. [/advertising]

...with the exception of FFX-2 HD which is here for a totally different purpose, as it's quite certainly THE most fun game I ever played, and yet I hardly see topics about the HD Remaster that don't focus primarily on FFX HD.

As for a fifth, hmm, hard to say. Can't think of one right off the bat.