There was a time when PUBG enjoyed massive domination. The early-access battle royale game was a huge breakout hit, with a record 3.2 million concurrent players on Steam almost one year ago. But its numbers have dropped off, and while it's still one of Steam's most popular games, it's nowhere near its peak. Meanwhile Fortnite is unquestionably the biggest game on Earth, and Call of Duty's Blackout mode brings another big name to the battle royale battle royale.