Fortnite

Fortnite's building system gives it a mechanical ceiling no other battle royale has, and it also made the game inaccessible to a lot of people. Zero Build, added later, removed it entirely and turned out to be a genuinely good shooter in its own right, which effectively made Fortnite two games with the same map.

Beyond the battle royale it has become a platform: user-created islands, licensed modes and a creator ecosystem that accounts for a substantial share of playtime. That makes it hard to evaluate as a single product, but the core mode is still sharp, still free, and still the most reliably cross-platform game on this list.