I would have ended Revenge of the Sith with Anikin on the operating table being worked on. The Darth Vader helmet is lowered onto his face and the camera is just looking at that. One breath in, one breath out, cut to credits.
The beauty of “noooooo!” is that in that moment the audience also cried out “noooooo!” upon hearing it and then felt, to some degree, the same anguish as Anakin.