Are we allowed multiples?
Deep tactical combat. Not hack'n'slash, something you need to put thought into. I don't mind if its first person or third person, but its got to be a system where my position and the position of my party members matters, where what classes I've bought and how I've built them matters, and where not every challenge can be completed by every character/set of characters, simply because they don't have the right skills for the job.
A world that properly reacts to the PC. Not a Skyrim world that doesn't change, outside of a couple of lines of text. Picking certain factions will lock others out, and major choices can change both the face of the world, as well as the personal stories of those around you, come end game.