The only game that comes to mind for me is one of the Baten Kaitos games. Maybe my memory is failing me, but I remember those being fairly good and interesting games. They're no Persona 4 in terms of quirkiness combined with actual quality, but what is really.
Maybe Persona 3, but that would just feel like a P4 endurance run 2.0. Would probably lead to too many comparisons between the two and I can't imagine a P3 endurance run winning those comparisons. Plus part of the fun for me was watching the guys figure out the mechanics of the game. By knowing Persona 4 they're already pretty well past that learning stage in Persona 3 as well.
I wouldn't mind seeing Dark Souls, but the only issue with that would be that whoever is playing would have to truly want to play it. Its not really a game you can play just because people want you to play it. If they went into it with the wrong attitude and then start failing over and over again I could see it becoming boring and frustrating very quickly.