Even then, the DS is pretty specific for its dual screen setup, and makes playing on anything that isnt a DS or similar form factor feel pretty unapproachable. Have you tried other consoles, like the PSP? Since it only has one screen, and does not have touch support, it can feel like it was designed for normal console style play.
Its only a suggestion, there may be other reasons he doesn't play. Maybe the games just don't interest him?