Why are people arguing over how powerful Revan was or Yoda was or Sithari or whatever?
That's all irrelevant to the actual debate.
I don't think anyone is denying that Revan would beat Nihilus in a traditional fight. Revan is, after all, a master swordsman, and Nihilus did in fact suck.
The only question is, could Nihilus use his drain power to kill Revan? And the answer is a most probable yes.
God is a placebo with nasty side effects.