Around 1972 I got into board wargames (AH, later SPI); about a year later I moved on to miniature wargaming (ACW, Medieval, Victorian Small Wars). I anjoyed these, but there were so many arguments that came up (we were all in our early-to-mid-teens) about winners, losers, line-of-sight, etc., that the whole process was getting frustrating.
Then Brookhurst Hobbies (blessings upon them) sent me their August catalog. There was an ad in there for a new type of wargame involving dragons, heroes, magic swords, and quests for treasure, but not needing minis or a board, being played with paper and pencil. The description was very sketchy, but I sent away for it. Just as I was about to leave for a Labor Day weekend Boy Scout campout, that glorious brown UPS truck pulled up with my package. That weekend, when everyone else was hyped over CB radio and getting blue ribbons, I was learning to speak a new language involving hit dice, armour class, and black puddings that you didn't eat...
And I haven't looked back in 30+ years.
Admittedly, though, I have been fairly profligate in the number of systems I have worked with, though. I dropped D&D about the time it became AD&D ("1st edition") in favour of RuneQuest, Traveller, Champions, Chivalry & Sorcery and a host of others. Since then my "game of games" has shifted several times, including the above-mentioned RuneQuest, Pendragon, Cyberpunk, and Ars Magica. Currently I am playing a 7th Sea variant (where I took the rules and scrapped the horrible map and historically bizarre collection of nations).