wellllll, that’s a (hilariously) contentious topic. I’m of the opinion that there is no one “correct” aspect ratio, as CRTs are analog devices and therefore have varying levels of overscan, as well as no real concept of horizontal resolution, so as long as you’re in the general ballpark and it looks right to you, you’re as “correct” as anyone. (pay no attention to the “circles are round!!” crew; in-game artwork is a poor and inconsistent guide)
Other people, however, are of the opinion (and they’ll tell you it’s not a matter of opinion but fact!) that there is One True Aspect Ratio that’s based on a calculation derived by the console’s native dot clock multiplied by the horizontal resolution including horizontal overscan minus the square root of the velocity of a load-bearing swallow (last part added just to poke fun, in case it wasn’t obvious). To these folks, 4:3 and 8:7 are as incorrect as 1:1, 16:9 or 200:14.
Now, to be clear, I think these people with their dot-clock-based calculations are as right as anyone else (but not moreso!), and if it makes them feel better to do a bunch of math to justify their choice, more power to them, but this is a mythical, nominal aspect ratio that they propose (and changes with each video mode, among which many consoles switched frequently), which does not reflect what anyone actually saw on their display beyond random chance.
tl;dr: go with what looks right to you.