So with the introduction of SDL, I was pondering about more FOSS games making their eventual way to Lakka in the form of cores and I first thought of the GCW-Zero (archive link) which had many good games, but the hardware itself was flawed (not keen on the controller ergonomics). My logic is that if they can be ported to a tiny MIPS device with 256MB of RAM, they can run anywhere. 
So here’s a list of core game suggestions, many have a Windows port so you can try them out.
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Meritous - Rogue-like action game, that I found quite enjoyable to play.
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Neverball/Neverputt - Super Monkey Ball-style game where you rotate the playing field to guide a ball through a maze. Neverputt is a golf-style game with a similar approach.
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Powder - Powder is a rogue-like designed originally for the GBA and then ported everywhere. Like Rogue (and Nethack) it’s challenging, yet engaging.
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[Griffon Legend] (https://github.com/dmitrysmagin/griffon_legend) - A fantasy action-RPG.
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[FreeDOOM] (https://freedoom.github.io/) - DOOM-like shooter that uses free assets as well as the engine.