This is a good list, and there are some games on here I've never heard of. That said, I would suggest the addition of Xonotic[0] to the 'first-person games' category, and Luanti[1], formerly MineTest, to the 'sandbox games' category.
And Speed Dreams and Stunt Rally to the racing games category. I guess we should open issues (or PRs).
Shout out to Cube for giving us the ENet library.