May not be as good as an F22A, but numbers have a quality, all of their own. You maybe able to shoot down six opponents but seven eight or nine can still get you.
Would the US, sell the F22 to anybody outside the USA? if not I would not like to bet on the outcome of 1v1 between an F15C and an SU30. That would possibly come down to either a BVR kill scenario or pilot skill in a close in fight.
Having seen Anatoli Kvachutur fly the SU27, in my opinion it would give an F15 a serious fight and I suspect even an F22 if the sukhoi has their version of thrust vectoring.