SteamDB says Rimworld, but I’m almost certain it’s actually Fallout: NV, as the Nexus launcher at one point bypassed Steam and so those hours aren’t represented. I have about 1100 hours in Rimworld, but probably closer to 3000 in Fallouts 3 and NV.
Lol I somehow completely forgot about Guild Wars 2. Pretty sure my age in that game is over 2 years of active playtime.