Player options is a good idea. If I'm playing an old game (i.e. graphics aimed at much lower resolution than I want to run at) I'd rather play in a letter box but someone else might be happy for the graphics to stretch and look blocky to fill the screen.

Aspect ratio is the fundamentally unsolvable problem, at least fairly. You end up letting one ratio see more of the world on-screen than another unless you allow a square graphic to be stretched to a rectangular shape. Again, I prefer to letterbox here but it is subjective, not "correct".