What are the 5 best games to introduce someone to PC games?

This year, I re-established contact with a childhood friend and brought him back to PC gaming. I played several recent games with him, some casual multiplayer games (Back 4 Blood, Chivalry 2) and rekindling things we loved in the 90s (MechWarrior 5, Streets of Rage 4). I think many of you have had this experience, because our hobbies have become more and more mainstream over time.

Looking at PC gaming through the eyes of a novice made me think: What is the best way to get someone into PC gaming today? Is it better to give them homework and history, the core game that makes PC games unique (whatever that means), or something easier for them to enjoy immediately?