Well it's just the amount that declare it on the partner portal and their store pages and are currently publicly viewable.

Said number is roughly 1354 currently if you go around counting things like DLC and Demos distinctively.[1]

The majority being games with ai-generated assets, with a small number (~99 currently) being live-generated content like chatbot interactions.

https://steamdb.info/search/?a=app_keynames&type=-1&keyname=...