Correct pronunciation: "Day-S-Eks"
Incorrect pronunciation: "Deuce Ex" "Dee-us Ex" "Day of Sex"
Not all videogame mispronunciations can be blamed on our ignorance of the Japanese language. Nope, some of them can be blamed on our ignorance of other languages as well... Latin, for example.
In this case, the mysteriously unspeakable title actually worked in the game's favor. When those in the dark finally got around to asking their smarter friends for a translation, they must have been awfully disappointed to discover the title referred to an act of God and not gambling or pornography.
Above: Even the game's protagonist looks confused. We feel better