Whether you think Fallout 4 is good or not, here's a value that can't be argued. A lot of people are playing it right now. So much so that it has destroyed previous records for concurrent players actively playing a non-Valve game. As of this writing, it has even surpassed Dota 2's active numbers for the moment.
The peak of the game as of now is at 445,546 and seems to be rising still. The peak probably won't touch Counter-Strike: Global Offensive's 585,510 peak today nor does it stand much of a chance at reaching Dota 2's peak of 765,504, but it's still incredibly notable. The previous record was held by Grand Theft Auto V this year when it amassed 360,000 concurrent players at the same time. An 85,000+ jump in the record is enormous.
There have been quite a few mentions about how the game is buggy or doesn't quite meet the expectations people have. It certainly didn't get away perfect in our review, but considering the hype and buildup around this entry of the franchise, it's really not hard to see why so many people are on board to make this one of the most played day-one games in history.
We collected these stats from Steam's stats and rankings page
(UPDATE)
As of a moment ago, Fallout 4 has topped the chart at #1 as the most active game on Steam right now. It's safe to say that won't not last forever, but for now, nuclear war is king of the hill.