[Matryx]

Generally a Role Playing Game is where the player assumes a different 'Role'
In SE4 you assume the 'Role' of the commander / omnicron etc of the the race you control.
In Dungeons and Dragons you assume the persona of the character you play.
Generally, if the option exists for an immersive personality switch it can probably be called a Role Playing Game.
Games such as Unreal, Quake etc could not be called Role playing games because they do not develop the characters to any degree of have the ability by which you assume that role affect the course of the game.