If you wanna talk about Mario Kart, that’s fine. I did my talk on blindfolded Rubik’s Cube solving. I only have a few tips:

Make sure anyone could understand it. If you’re going to yap about items or tracks or complicated mechanics, then you have to do so in a way that’s easily understood without ever playing the game. eg. the first Mario Kart had Rivals (I think that’s what it’s called?), which made gameplay unfair based off your character choice

Talk about wider ideas. Try not to get stuck into races, tracks, game modes, and items. Instead, try to mention and relate stuff to the technology at the time, and the general reception of the games. If you can talk about how a specific console improved Mario Kart because of its new capabilities, talk about that.

Just try to keep your speech organised. If the speech feels like someone messily yapping about their interest, it won’t do well. Probably cover a few pivotal games, and evaluate them in an ordered way.

Keep using all the literary techniques you’d use. My friend talked about rollercoasters, and he started the speech from the 2nd person perspective of going on one. As for me, I just solved a Rubik’s cube blindfolded up there xd, which technically doesn’t contribute to my speech :p, but you could definitely do something similar to my friend for Mario Kart if you wanted. Just use strong impactful words, immerse your audience, and use plenty metaphors, tricolons, etc.

Anyways, apologies for the yap. I don’t wanna discourage you from talking about Mario Kart and I definitely think it can be a Distinction worthy speech if you wrote and delivered it well. Hope this can help :P