@mr-tom: I've broken your post up to make it easier to address:
mr-tom: Dragobr, SirPrimalform & AlexY - Apologies - I did not mean to imply that. Some will run, some will not.
You might have some games that don't run, but I don't see how that could have anything to do with them not being widescreen.
mr-tom: Some, whilst running will be unplayable or sufficiently difficult to interact with that the fun is gone.
Again, I'm not sure how a lack of a widescreen resolution could make the game unplayable.
I'd appreciate if you could elaborate on what could make the game unplayable or difficult to interact with?
To make sure we're talking about the same thing, I've attached a picture showing how The Curse of Monkey Island (a 640x480 game) looks when running on my 1366x768 (near as damnit 16:9) laptop.
mr-tom: In each case, it will be useful to determine the likely user experience prior to choosing whether to spend money on it.
I agree here.
mr-tom: Vestin - Sadly, I suspect we are unlikely to agree. Within my country, the law is that any product sold must be fit for its stated purpose. Whilst many games will be, some could be unappealling on a widescreen and as such, could be considered unsuitable for a sizeable portion of the population.
I don't see how looking unappealing on a widescreen makes a game unfit for it's stated purpose. You might as well complain that it's unfit for it's stated purpose because it's too hard, or you don't like it. Looking unappealing is a completely subjective thing and is therefore completely irrelevant to the law.
EDIT: Forgot to attach the image..!