The concept of cross game play  gives players abillity to to us same games when they play on their server. Now the Sony has joind the club, here is the partial list  found over at DigitalTrends.  This feature is still in development, but with no doubt it will continue to get new games  coming in.

Here is the current list

Full cross-platform support

• Fortnite: PS4, Xbox One, Switch, PC, mobile
• Dauntless: PS4, Xbox One, PC
• Rocket League: Xbox One, Switch, PC, PS4
• SMITE: Xbox One, Switch, PC, PS4 (September 17)
• Paladins: Champions of the Realm: Xbox One, Switch, PC, PS4
• Realm Royale: Xbox One, Switch, PC, PS4 (October)
• Call of Duty: Modern Warfare: Xbox One, PS4, PC (October 25)

Partial cross-platform support

• Minecraft: Xbox One, Switch, PC, mobile
• DC Universe Online: PS4, PC
• Aragami: Xbox One, PC, Switch / PS4, PC
• Ark: Survival Evolved: Xbox One, PC
• Astroneer: Xbox One, PC
• Blobcat: Switch, PC
• Brawlhalla: Switch, Xbox One
• Chess Ultra: Xbox One, Switch, PC / PC, PS4
• Deep Rock Galactic: Xbox One, PC
• Dick Wilde 2: PS4, PC
• Disc Jam: Switch, PC / PC, PS4
• Eve: Valkyrie: PS4, PC
• Final Fantasy XIV: A Realm Reborn: PS4, PC, Mac
• Full Metal Furies: Xbox One, PC
• Games of Glory: PS4, PC
• Guns of Icarus Online: PS4, PC, Mac
• Happy Wars: Xbox One, PC
• Hearthstone: PC, Mac, iOS, Android
• Hero Siege: PC, Mac, mobile, Switch / PC, Mac, mobile, PS4
• Hex: PS4, PC
• Hover: Xbox One, Switch, PC / PC, PS4
• Kabounce: PS4, PC
• Mantis Burn Racing: PS4, PC / Switch, Xbox One, PC
• Mushroom Wars 2: Switch, PC, Mac, mobile
• NBA 2K Playgrounds 2: Xbox One, Switch, PC
• Next Up Hero: Xbox One, Switch, Mac, PC
• Overload: Xbox One, PC / PS4, PC
• Phantasy Star Online 2: PS4, PC
• Pinball FX 3: PS4, PC / Switch, Xbox One, PC
• PlayerUnknown’s Battlegrounds: PS4, Xbox One
• Pox Nora: PS4, PC, Mac
• Pure Chess: PC, 3DS
• Rec Room: PS4, PC
• Riptide GP Renegade: Switch, PC / Xbox One, PC
• Roblox: Xbox One, PC, Mac, mobile
• Siegecraft Commander: PS4, PC / Switch, Xbox One, PC
• Sniper Elite V2 Remastered: Xbox One, PC
• Spacelords: PS4, PC  / Xbox One, PC
• Sports Bar VR: PS4, PC
• Star Trek: Bridge Crew: PS4, PC
• Street Fighter V: PS4, PC
• Square Heroes: PS4, PC
• Super Dungeon Bros: PS4, PC, Mac / Xbox One, PC
• Super Mega Baseball 2: PS4, PC / Xbox One, PC
• Trailblazers: PS4, PC, Mac / Xbox One, Switch, PC
• Treasure Stack: Xbox One, Switch, PC
• Tooth and Tail: PS4, PC, Mac
• Ultimate Chicken Horse: PS4, PC, Mac / Switch, PC, Mac
• War Thunder:  PS4, PC, Mac / Xbox One, PC, Mac
• Wargroove: Switch, Xbox One, PC
• Weapons of Mythology: New Age: PS4, PC
• Werewolves Within: PS4, PC

Xbox Play Anywhere crossplay

• Crackdown 3
  Fable Fortune
  Forza Horizon 3
  Forza Horizon 4
  Forza Motorsport 7
  Gears of War 4
  Gears 5
  Gwent: The Witcher Card Game
  Halo Wars 2
  Killer Instinct
  Sea of Thieves
  State of Decay 2
  Zoo Tycoon: Ultimate Animal Collection