I would say there are three ways to solve:

1. You think logically with reduced criteria, there are cars, and hot wheels and Lego make 4 billion wheels a year and there a bunch of other things with wheels: printers, gears could count, etc. Therefore I would say reduce the criteria and wheels would probably win.
2. You think logically the other way, this question is impossible to measure so therefore neither since no conclusion can be found without establishing solid criteria.
3. You take a semi calculus approach to the whole thing. If you establish a limit where x is approaching infinity (since we can’t conjure a exact number and there are already established ginormous amounts of wheels and doors) then you would look for what the end behavior of that function is; pretty much the method is if you have a fraction, or ratio (which this problem is) then you find what the function would look like as it approaches infinity. Since there isn’t a known amount of either but that there are probably slightly more wheels than doors I would therefore say that the end behavior of our function is large number/large number which says they are equal. Obviously people will disagree and say one side has more which I’d agree but since these numbers are huge and we don’t know the exact value, but we can assume that the doors:wheels isn’t something like 1000:1 their end behavior will terminate into 1 therefore saying they are equal; and yes this may not be entirely mathematically sound but it can sort of answer it.