When I use the terms, I'm usually referring to the feel of a particular rule, sub system or even entire RPG rule set, not necessarily players.
"Gamist" is a rule which looks more like a move in a chess game, abstact and having little to do with "the real world" or the current scene or overall story in the RPG.
"Simulationist" is a rule which is trying to reflect how something works in the real world, often looking more like a physics equation for acceleration or bank interest.
"Narrative" is a rule more akin to a direction in a movie script, designed to push the scene or overall story forward, or enable more improvisational roleplaying.
Any RPG includes all of these elements, to varying degrees. Applying the various labels to players just describes which of these elements they enjoy focusing more on (which, in my experience, can even change for a particular player during a single game session.)
Taken in order, GSN terminology kinda describes the evolution of RPGs. Take a game of chess, add rules to simulate factors like the pieces position on terrain, troop strength and a degree of uncertainty (typically via dice) for attacking the opponents pieces (like war games re-enacting famous battles), then add ways for players to narrate the interaction of their pieces with the game in detail, and you've got an RPG.