TNG was the first star trek I was exposed to, and for a long time, it was the only one I liked. When I got to my late teens, I gave TOS another shot and fell in love. Now TOS and TNG are both my favorites, but TOS just feels more important, and iconic. I give TOS a slight edge these days.
Would I have become a TOS fan without TNG to pave the way? It's hard to say. I think I would have, since my father was a big TOS fan since he was a kid. If there had not been a TNG, I think he would have turned me on to it. I don't think I would like it as much as I do now if it hadn't been for TNG, though. I think TOS and TNG really enhance eachother. The Trek Universe feels so much larger when you take both into account.