Not sure I entirely agree. Myst had mass market appeal because it was one of the first crossover/"casual" games that didn't require the player to immediately start killing things within a few seconds of starting up the game. I could let my mother play Myst--I don't think I could let her play Half-Life. For one thing, if trying to show her Minecraft taught me anything, it's that the paradigm of separated Looking vs Moving (i.e. WASD+Mouse) control is one too many things to juggle for your average non-gamer.