Oh goodness, uh. Well, franchise-wise, definitely the Sims. I started playing Sims 2 when I was ten or so and I've put countless hours into 2, 3, and 4 since. Same with Minecraft and Spore; no idea how many hours I've played, but I've owned them for 8+ and 10+ years, respectively.
According to Steam, my most-played games are: Binding of Isaac/Rebirth (500 hours between both games), Don't Starve (120 hours), Skyrim (106 hours), Stardew Valley (104 hours), and Terraria (82 hours).