is there a game he's played a lot that you haven't really (maybe something from childhood or w/e), my half-assed way of dealing with a vaguely similar (although it really wasn't that I crush in all games but that we both got butthurt losing) was to find stuff where person A has the edge and person B has the edge, even if its just due to familiarity with the game and where it's sort of almost accepted who's gonna win beforehand and aim of the game is just making it a bit of a challenge for them or whatever. to be honest it's not a great solution.

How much does he care about losing? If I'm in a situation where I'm expecting to lose then my ego doesn't mind so much, and I quite enjoy the challenge, really my only fear/concern in that area is that I'm boring the other person.

Iunno how easy it would be to get the point across that even if you are better in all games than him that doesn't paint a complete picture of intellect or intelligence, as you said you're interested in game theory and the like and probably expend more practice/effort working on improving there (even if that just means more conscious thought on decisions while playing), which is maybe a skill like anything else rather than some kind of indicator of who's smarter.

you already answered my one liking it in the pooper related question in another thread ty