• Marble Racing - Tracks are created, and bunches of marbles are rolled along them.
• diecast_racing - Similar to marble racing, but using model cars, and simpler tracks.

Games where it's fun to just watch—where I/'ve enjoy/ed just watching. Particularly for watching the game in-person, rather than a stream.

• Nintendo Pocket Football Club - A cute football management game. Matches are entirely simulated, and there are nice details in the animations.
• Pro Evolution Soccer 2017 - There is a 'sim' mode where you just watch your team play, all in the same engine as the regular game.
• Soul Calibur II - You can pit CPU fighters against each other. Pretty fun!

• Attract Mode - Twitter bot that posts replays of CPU v. CPU fighting games. The linked README and this forum thread list relevant games: Fighting games with a CPU Vs. CPU "Watch" mode
• SaltyBet - Bet fake money on CPU v. CPU MUGEN matches.
• Ambient Play Systems (In and Outside of Games) by Flan Falacci