The definitive version of Gen 4. It has the Distortion World and a solid difficulty curve.
Because the demand is so high, scam websites thrive on this specific keyword. If you download a file labeled Pokemon_X_USA_NDS.7z , you are almost certainly downloading malware. Here is what those files usually contain: pokemon x y nds rom
Search for Pokemon Blaze Black 2 or Pokemon Storm Silver . These are "enhanced" rom hacks of the DS games that add Pokemon from X/Y (like Sylveon and Greninja) into the DS engine. This is the closest you will ever get to "Pokemon X on the DS." The definitive version of Gen 4