When you started gaming, it was obviously with something. I've noticed that some people started out with one RPG, but very quickly dived into a whole variety of games quickly, but others stuck to a single game for quite a while before diversifying. What kind were you?
RPGPundit
The former, as far as my beginnings are concerned.
I was introduced to RPGs via AD&D and the Temple of Elemental Evil. After a few months, the DM offered me the Dark Eye RPG for Christmas. I ran games for some time with it, then came back to D&D via Mentzer.
It's only later that I chose to stick to one particular RPG. It was Stormbringer, for two/three years. Then I ran Vampire The Masquerade with a single campaign/chronicle for eight years. Longest running campaign I've run.
The OGL period is apart, I think, since I stuck to 3rd ed the whole time (and still do) but happily played, ran and mixed stuff up when it came to the miriads of OGL variants out there.