front mission series
super robot wars series

only those two come to mind... a lot of older "classic" SRPGs really are rather bland in terms of plot. it took nippon ichi to break the mold, and they're pretty much the only ones who make SRPGs these days outside the long-running series, too. (i take it you've played every game by them, and not just disgaea? though the others may not have gotten an european release)