For a specifically “nudist” game, with overt nudist themes and possibly setting?
The best option would be either a life sim (similar to the sims or second life), a business management sim (similar to zoo or rollercoaster tycoon), or a visual novel of some kind.
For a game where you could be naked, perhaps with some nudist themes, but setting agnostic (not tied to a specific setting/kind of setting)?
Frankly skies the limit, an RPG would be a good choice because them nudism can become an “option” for the player. But an action game or shoot-em-up (like Star-Fox or The Gaurdian Legend).