The first RPG I Gamemastered was most assuredly Basic D&D, although I keep thinking it was the edition after Holmes' version. This can't be of course, since I ran my first game in the Summer of 1978.
I only got to play D&D as a player from August of 77' until just before the Winter Holiday vacation from school in December of the same year. Following the holidays, my life became somewhat complicated and I didn't have as many free weekends as I would've liked.
I didn't see an RPG again until June of 78'. It was then, when I attended Summer camp, and a friend of mine had the D&D game there that I got to scratch the itch that had been building. I saw the box set my pal had, and I mentioned I'd played the game before, and I was immediately designated the GM for the group that wanted to play it.
In 37 years, only the game has changed. The joy of gaming and especially Gamemastering is stronger than ever, and I wouldn't have it any other way.