A record of sorts was broken last night as evident in the stats section of Steam. It turns out that Fallout 4 instantly passed Grand Theft Auto V for having the most concurrent players simultaneously with around 409,000 players online simultaneously. Grand Theft Auto V had around 360,000 players at most and before that, The Elder Scrolls V: Skyrim held the record.
But there is one catch. A big one. This record excludes Valve titles. Counter-Strike: Global Offensive often have around 600,000 gamers playing simultaneously, and for Dota 2 it's around 800,000. Of course, the latter is free-to-play. Still, the number for Fallout 4 is of course really impressive. Still, whether you want to call it a record is up for debate.
Thanks, Destructoid.