Hiya!
1981, Dungeons & Dragons Basic Set 1 (Erol Otis cover; Tom Moldvay version). Although I did play the '77 version (the Holms version) for a single game, iirc (me and my best friend who bought it) very quickly after playing the Moldvay version for a month or so. I (we; me and my friends and father) stuck with the Moldvay version.
After that, Star Frontiers, Top Secret, Marvel Super Heroes, Gamma Word (in that order)...then Warhammer Fantasy Role-Play, Runequest (very briefly) and Warhammer 40,000 (which we thought was an RPG, because we had no clue about wargaming; we learned...and then promptly kept using it as an RPG in stead).
^_^
Paul L. Ming