ScienceGameCenter is described as 'The goal of the Science Game Center is to demonstrate to teachers, scientists, museums, and parents the myriad ways games can be used to improve education in math and science' and is an website in the Education & Reference category. There are more than 50 alternatives to ScienceGameCenter, not only websites but also apps for a variety of platforms, including Windows, Mac, Linux and Android. The best alternative is Steam, which is free. Other great sites and apps similar to ScienceGameCenter are GOG.com (Free), Humble Bundle (Paid), itch.io (Free, Open Source) and Lutris (Free, Open Source).
itch.io gives you the ability to design a page where people can download games you have uploaded. You can optionally put a minimum price on your game (which can be 0), giving people the opportunity to pay you what they think you deserve. All files and images are hosted on itch.
The Epic Games store is now open, featuring games from other developers. Epic's goal is to bring you great games, and to give game developers a better deal: they receive 88% of the money you spend, versus only 70% elsewhere.