I'm a descendant of Chicagoans and my brother actually lives there now. That said, Chicago hot dogs are not the greatest fucking thing to do with a hot dog. If you're going to pile some shit on top of it it should be chili, onions, and some cheese.
Not that they're bad, but it's like a worse argument of "NEW YORK PIZZA IS ONLY AND BEST PIZZA" but with a much, much weaker case. But the NY pizza shit is stupid too.
And honestly a nice all beef hotdog with mustard, onions, AND KETCHUP is pretty fuckin' nice. Is it the best? Who knows. But the ketchup and mustard in tandem is good.
If I want to make you guys upset though when I was a kid I'd melt a kraft single on it in the microwave then slather a little ketchup on it. On a bun, of course, I'm not some keto weirdo.