"acceptable quality" is very broad and subjective. I don't think you'll have much luck convincing a court a game is objectively bad. (unless the game actually crashed like where somebody mentioned in KOTOR)

If you take a game back to a major retailer like Target or Big W, they won't accept it with the seal broken unless you tell them there is something wrong with the physical disk or cartage. They won't accept a return if you just tell them you didn't like it. (in my experience - also not an expert on this either)

My point is just that their broad "we don't accept returns, ever" policy in the UK is not legal in some jurisdictions, and nothing about returning a game because you don't like it. How that's interpreted is, of course, a matter of convincing the courts but the language Nintendo uses in the UK is not applicable worldwide, as many other companies have been raked over the coals for trying to do the same. Note that the wording on the UK page definitely excludes things like KOTOR II from being returned!