Neotron Games: Treasure Trove of 2D Games
Neotron Games
These guys have compiled quite a selection of quality, complete games. Actually, to such an extent, one could say that they are one of the most prolific open source game devs out there, even if not all of their works are completely “open”.
Most of their games are compatible with the GPX-Wiz, and hopefully the Pandora once Bennu, the language they use for developing their games, gets an official port.