For me, it's all about finding clues. for example, at Fallout, you have to find clues about waterchip, GECK or a man. and while you are finding clues about those, you also find clues of something more important or more urgent event you have to prevent. how about beth's pseudo RPGs? while there are no real clues to do something, the game still requires you to do some chores to feel like finding clues. how about other genre of RPG? while playing old Wizardry, I have to draw maps. why should I draw maps? because I need some clues to check where exactly I am. many old gamers complain about automap system because it removes finding clue part which is an important part of an RPG. So, in conclusion, I think finding clue can define RPG.