Playnite

Hands down the best game launcher you will ever find. It's completely free, easy to request features and report bugs.
The dev is very nice and it shows how much he cares about providing a the ultimate free game library on the internet.
Very intuitive UI and easy to use and easily add Games or programs and metadata from various sites.
Able to add games from Steam, Uplay, GOG, Blizzard, etc.

Superb games manager to unite your games library. Main feature: organisation of games which are only in your cloud library and not locally installed (e.g. steam).

FINALLY a good game launcher.

Brings together games from other platforms in a very automated and convenient way, even works with emulated titles. Also capable of importing steam categories and filtering games by tags and a slew of other parameters.

It's the best games library manager. It's free, open source, and can be extended by plugins. It's highly customisable. It handles emulated games well. It's under very active development and the dev responds quickly and effectively to feedback.