For me my highest priority is character creation options. How I view myself affects the entire game, and can give entirely different perspectives on the same events. I simply cannot ever have enough character creation options.
My second highest priority is the choices and consequences. These give the differences substance, meaning, and replay-ability. I also feel like developers these days (not just RPGs) are too afraid to use consequences. They are just as powerful of a tool as rewards, and without both sides of the coin a world becomes shallow and unbelievable. Villains and victims aren't secretly out to just feed you loot. Sometimes doing good is it's own reward, and sometimes it's the much harder path. Being evil and selfish might get you more gold, but you probably won't make as many friends along the way.