what videogame do you have the most hours in?

Fallout New Vegas for sure. On Steam I have 467 hours logged and I played probably another 150 hours on Xbox 360 back in the day. If it wasn't so hard getting Vortex working on Linux I'd be starting another 30+ hour save today.

After that is Project Zomboid with 460 hours but I feel that's less shocking in a sandbox game.