Well, see, there's nothing quantifiable for Shan's powers & abilities. We know she has potent battle meditation, but that's not viable for this contest. I don't recall any other cutscenes demonstrating her skills apart from this one:
Based on that, you could make the argument that the Sith Bastila killed might have been one of Revan's elite bodyguards, and therefore by no means average.
But, after this, it's all reputation and plot based assumptions for Shan, which paint her in a relatively positive light.
In any case, ROTS Kenobi would defeat AOTC Anakin. And I see Bastila > Unduli, but not by much at all.