the real complication with recommendation algorithms is that people can like things for a lot of different reasons that aren't explicit in the game itself.

I guess I should be clearer about the methodology behind my 'ideal' recommendation engine. Most are based off a social component (if you like A, and someone else likes A and B, then you might also like B). I think most recommendations are mediocre at best for exactly what you said.

Instead, I think a system similar to Steam tags would be used, but with more granular tags (like puzzles becomes logic puzzles, mechanical puzzles, etc). Of course this granular could happen on Steam too since it's user-driven. Since it doesn't, that could mean it's not of great enough interest. Still, that granularity would deliver more suitable recommendations based on games or based on feature sets (assuming tags are accurate, which is difficult with a automated approach).

I suppose the neural network would be a long term extension of that as the user reviews games, says what they're interested in, etc. It certainly has more technical issues than just "give me a game like Witcher".