Even if the first true RPG I got my hand on the red box D&D first, many of its concepts I did not understand. You have to jump back to 1984... Many of the concepts therein I did not understand. Literally. Did not understand. Back then while I spoke English, I was far from fully fluent. The basics, I got.
All that changed at my 12th birthday.
On that day, I received the "Initiation au jeu d'aventure" (trans. Initiation to the adventure game) for the "L'Oeil Noir" RPG. It has since attempted to translate from German into English as "The Dark Eye RPG" with limited success. However if you were a French-speaker and into RPGs in Montreal in the mid-80s: you knew and played that game. It was light, easy and fun. Plus the rule book was the size of a Fighting Fantasy book. Within the box were a rulebook, an adventure book, a D20 and 3d6. All you needed to play the game. I've made reference to the game on my blog here and there.
Like most early 1980s RPGs, it was a D&D clone. You could be a warrior, a wizard, an elf, a dwarf, or the more generic "adventurer". The game was quite simple, but had a number of interesting things within: the attack and defense numbers were assigned by the player each round, there were no alignments, to cast magic the elf or the wizard had to speak out the "magic" formula (I still remember the fulminictus or medousa spells), a mana system for magic.
The adventure book had two short adventures as "example". One was a solo and one was for a small group.
The adventures written for that game system are quite good, and are still in my library. I refer to them regularly, if only to look at the pictures.
I still love this game.