7: Most “Intellectual” RPG Owned. I can’t decide whether the quotation marks are meant to be ironic or generalizing. Most RPGs that I’ve played seem to be more about action or emotion than intellect. Many have sophisticated settings or adventure plots, but that doesn’t strike me as “intellectual.”
Some, like Eclipse Phase, have some nifty SFnal ideas I suppose you could call intellectual. Others take more “intellectual” approaches to the supernatural, like The Whispering Vault. Some, like The Extraordinary Adventures of Baron Munchausen or, in a different sense, The Dying Earth or the Amber Roleplaying Game, require the players to be quick and clever to fit into the milieu. Others are just hugely pretentious (but often still fun).
Planescape, as Zeb Cook initially described it, was about “philosophers with clubs.” While in practice the adventures were often every bit as action-oriented as other D&D scenarios, the intent to pit factions against each other with an emphasis on their different views of the cosmos is a sort of intellectual paradigm.
So I’ll say Planescape.