Steam

I would say that while it is a monopoly, it monopolizes something which doesn't make much sense to be decentralized. Having multiple launchers for games, and making some games exclusive to some launchers but not others etc. is annoying as hell and is only a good thing for the executives and investors behind these companies at the expense of everyone consuming the product.

Having one corporation be in control of the distribution platform for most if not all games is also very troubling, but until it's possible to have a democratically owned open source distribution platform, there's no other good way.