From the Ep 3 book it turns out that Palps is the greatest sith lord, screw all the EU nonsense he is it.
Regarding vader, even though i hate the whole bit with midichlorians to explain the force, it serves as a good explanation as to why vader is much less powerful post immolation, than pre.
Revan is lame all his "power" is hearsay and in the game if you autolevlled him badlay he is a crappy jedi/sith.