It's just the same usual blockchain problem over again. The blockchain part itself that allows some token that you can trade around, that's well established. The part where that bridges the gap over into something real or useful (even something that's already very digital like a video game skin) is where it all collapses.
The usual problem type I seem to see is something along the lines of: "to make this work, you need to introduce some trusted party, and then if you're going to trust them anyway you might as well have just had them run a database." For games the more salient point is that to have your "cross-game transferable items" system work, you need buy-in from the developers, who generally all already have jealously-guarded disconnected microtransaction systems that they're making enormous profits off of and they're not really incentivized at all to let other people play in their sandbox. Let's ignore for the time being the mechanics of actually making cross-game, cross-engine, cross-genre items work at all in the first place.
The hope for proponents would seem to be to jump-start the ecosystem in games they create and create a groundswell of gamers who demand that big titles work with the blockchain system, but that just doesn't seem realistic for a variety of reasons. Even within the hypothetical universe of NFT-ized games, the same kinds of incentives (and technical issues) are likely to throw up similar barriers to interoperability between different games.