Well, Brutal Legend is more RTS than SRPG, but I don't remember it having chapters. Its also played from a fairly unique perspective (this isn't Warcraft or Command and Conquer!) .. unfortunately, I kinda get the sense you want a game you can basically leave on all day or night and have nothing of any significance happen until you actually pick the controller up again and start to play.
Have you looked at Rainbow Moon?
Other than that, I'd suggest checking the PSN for some PS1 and PS2 "classics" to see if there are any RPG's you've missed.