Then he'd be half right. If you say 'World War II' never existed, even though there is evidence. You'd be wrong. But even if you use the latest cutting edge blah blah blah graphics for your game, there will always be someone who says 'this svcks'. But you can't prove or disprove that the graphics svck. It's all semantics basically.
Can you change his mind? No.
Can you prove him wrong in general, yes.
It may be his opinion but it isn't right in general. A guy can hate 2001: A space Odyssey, a guy can hate Citizen Kane, a guy can hate shakespeare, a guy can hate Mozart, a guy can hate everything artistically.
The opinion still isn't valid and only counts for his own perception of the matter. If a certain fact about a game/book/movie/other artpiece is generally aknowdlegde as quality. It is quality.