Cataclysm: Dark Days Ahead: Like Dwarf Fortress but post-apocalyptic survival horror. Endless Sky: top-down space shooter inspired by Escape Velocity SuperTux: inspired by Super Mario SuperTuxKart: inspired by Mario Kart https://en.wikipedia.org/wiki/List_of_open-source_video_game... and https://en.wikipedia.org/wiki/List_of_commercial_video_games...

Well:

- Supertux2, it got recently revamped, the quality skyrocketed. Much better controls and artwork.

- Supetux Advance, this is really great too.

- Retux (More Wariolike than Mario)

- Nethack/Slashem. A Roguelike more bound to interaction/exploration/mechanics than combat, but Slashem makes combat crazy with the Doppleganger Monk, which is basically a Shonen Manga, the role. (Dragon Ball/Naruto depending on your age).

- DCSS. Basically, not Nethack/Slashem, much more combat oriented than the Slashem combinatorics playing with the Monk a la Jackie Chan, this is more like an ARPG made a Rogue.

- Frotz/Lectrote/Winfrotz/whatver Z Machine interpreter and "All Things Devour". Spiritwrak, too. Great libre text adventures and still enganing because of weird mechanics.

- Frozen Bubble

- OpenArena.

- FreeDoom, better compiled with Deutex on daily builds.

- FreeCiv.

- OpenTTD today can be standalone enough.

- Frozen Bubble

- Minetest+tons of subgames such as Glitch, Nodecore...

- OOlite

- Speed Dreams. If the controls are hard, try the arcade mode. If the controls are still hard, get SupertuxKart, pick some real life car from the addons and get all the SD tracks from the inline downloader, they are several.