My contention is only that at the time they originally aired, TNG did better than TOS. And that TNG was phenomenally popular during that seven year period of time.
But my question is does that really matter in the grand scheme of things?
Also looking at all factors we can say the reason TOS failed during its original run is because it wasn't given a fair chance.
Keep in mind this whole discussion started when someone said TNG won because it stayed on the air for 7 years instead of 3 but you do have to look at extenuating circumstances.
I think neither series really wins, but people of course should not discount TOS because it only had 3 seasons. That isn't to say we should discount TNG either.
I don't think there should be a competition at all really.