Notes on Epic Games

"However, an increasingly large portion of the gaming economy now runs on virtual goods. The ability to take items, outfits, and more from one game to another will obviously increase the price a player is willing to pay on these goods. And if a user ever wanted to jump across digital worlds (as is portrayed in Ready Player One), it helps if all worlds use the same “physics” and “logic”."

This makes sense, but boy, this will never happen. As far as I am aware, songs from Guitar Hero and Just Dance aren't transferable from game to game. Same is true for players in Fifa Ultimate Team, anything you buy in Call of Duty, Battlefield and basically any game.

In many cases, the engines were the same between games. I just don't see transferable in-game purchases happen.

Valve and their marketplace system at least give players the ability to sell their items for funds, all without having to use a specific game engine.