Thats an open question if ever I heard one. I guess it comes down to what that means to me. For me a game I would give to someone else means a game I would suggest others to try and introduce them to the hobby.
For me then, there are two options and it would depend on the people. For the great majority of people, especially children or people in their teens I would suggest D&D, probably either 3.5 or 5th ed, more likely the latter nowadays. D&D is such an easy and manageable game to play to get into the hobby, it can be combat heavy if thats what people want (and it often is when they are new, because it’s easy to manage and understand), it has worlds to fit all tastes and everyone has at least heard of D&D.
For older people or people with more of a serious temperament, I’d use Call of Cthulhu. The advantage of Cthulhu is that it doesn’t require people to learn complex rules and it’s set in the real world, which gives people an easy basis for understanding the context of the game. Further, it relies far more on ideas than actions, especially in investigation heavy games, which is something many people would find easier than detailed rules governing combat.n