The rule n°1 of Unreal Tournament is "if can shoot works". even the Enforcer is powerful enough to take down a rocket launching bastard with some effort, a situation I've never been able to do on Quake 3 Arena.
My vote goes to Wolfestein 3D, is simple, was the role model, is has Hitler and works pretty well. I would have voted DooM 2 or Final DooM but as the levels progress they get more and more bullshit difficulty throwing hordes of monsters at you and not that many ammunition.