i love discussion. i just dont see a point in the current state of this discussion.
Jibb for example asked what if a faster player has less game?
well the answer is obvious, the majority of a game is to be measured by the fastest possible gameplay lenght.

if you really want to dfine by genre, simply define by movie genres. stop calling GTA a sandbox game. call it an action game instead. it may be hard to differentiate at first but once you get the knack of it its quite simple actually. because then you have already define what the player does in the game. a horror game? well he bloody well tries to survive the lurking horrors. action game? well things go down hot! mystery? puzzle solving ehre i come! adventure? well lets experience something you dont see everyday! and so forth.

basically: a game is to be played and the genre defines the playstile. you dont play an action game for a few puzzles it may have. action can go down with fists, gunfights or lightsabers for all i care. it still is action. add ONE secondary genre and be good with it. like action fighting or action shooting or battle action whatever. example:

skyward sword, fantasy adventure, 100+ hours of gameplay (and roughly 30+ hours of videos)

diablo 3: mystery fantasy, god knows how many hours of gameplay, a few cutscenes

heavy rain: mystery, more of an interactive movie

starcraft 2: scifi war strategy (war strategy is the secondary genre in that case) endless hours of gameplay a few dozen minutes of cutscenes

and so on. this is how I categorize games and how I explain genres to customers or people i meet who have no idea about gaming.
i figured thata term like survival horror is kidna redundand. as is teh term action adventure or point and click RPG. i mean, who in this world except a few of us knows what a "3rd person tactical squad based online shooter" is? in the end, it still is an action game...