AoE2 Expansion.
Woukd really like to see FOSS gaming community around that as well.

• Wurm: Unlimited, but without the adventure parts. Just building a farm, cultivating things, making food, beer and stuff, community life, villages;
• Football Manager, but make it highly customizable not only on teams and players, but on sports too - you want to create a ruleset for handball or water polo? Do it;
• Gran Turismo 2, but you can upload your cars, paintjobs and tracks. Cars could be highly customizable in order to support engine, transmission, suspension or rim changes, making these separate objects from the basic body for example. In that way one could build, for example, a Vauxhall Chevette with an electric pack, all-around independent suspension and rally tires;
• ETS2 with ProMods.

Magic Carpet and Startopia

• Super Street Fighter 2
• Street Fighter 3
• Starcraft: Brood War
• Warcraft 3
• Age of Empires 2
• Age of Mythology
• Grand Theft Auto 3/VC/SA
• Sim City 2000
• Counter-Strike 1.6
• Apex Legends

Elastomania