The answer depends on the age of the person being asked. Old Timers= Staubach. 90’s kids: Aikman. 2000’s : Romo.
Clutch: Roger Staubach
If you go back and watch Staubach play, it wasn't always the prettiest. There are some major games where Staubach looked bad while the defense kept Dallas in the game. However, when Dallas needed a play to be made, Captain Comeback got it done.
Accuracy: Troy Aikman
Aikman was great at putting the ball where it needed to be, thriving on the timing routes of Norv Turner's offense because of his pinpoint accuracy.
Moxie: Tony Romo
Romo didn't have the advantage of having great teams around him like Aikman or Staubach, but he was fantastic at keeping plays alive. Roger the Dodger was better at scrambling, but Romo was probably better at making something out of nothing with his uncanny feel for escaping defensive pressure.
Honestly because they played in different eras and for markedly different teams, it's hard for me to say who was the greatest. How would Romo do on those '70s teams or Aikman? How would Aikman or Staubach have handled Romo's situation? We saw Aikman's success go down in the late 1990s when we didn't have very good teams around him, but how much of that was due to age/injuries? I'm not sure Staubach every played on a bad team; imperfect ones, yes, but Dallas was a contender under Landry before Staubach became QB, reaching the NFL Championship Game in 1966 and 1967 and losing in the conference playoffs in 1968 and 1969 (Staubach's first year, but not as a full-time starter).