Video game genres shouldn't be defined by mechanics, controls, or intended "ways to play the game"

No worries at all. This is honestly one where I think I could get behind either side of the argument. If you like we could even do it again but reverse who is pro and con!Anyway, to rebut:PortalPeople certainly don't normally call Portal a shooter, but I think that;s due to you differing on what constitutes a shooter. A game isn't a shooter just because it contains a lot of shooting.Take any strategy game that contains shooting, like Command and Conquer of the Total War series. Despite there being a lot of shooting (My five units of 100 bowman might shoot far more in a battle than a CoD dude does in a level), no-one would ever classify such games as any variation of "shooter" using the standard genres, would they?This is because the already existing genres aren't as fallible and contextless as it might appear. Gamers know what makes a FPS and when a game does not contain the elements that fundamentally make something a shooter (Like targets you shoot to damge/score points, a central focus on shooting things, etc) they realise that it is no longer a shooter even if shooting is somehow involved.After all, the fact that pretty much every game involves some kind of strategy - whether it be circle strafing, when to use your super hadoken or how best to score a goal - does not make every game a strategy game.Movies, Books and GamesMovies and Books share the similarity that (Steve Jacksonish Choose your Own Adventure types aside) they are a form of media with a fixed narrative. When Dirk McShooty tries to kill all the terrorists in the room, in a book or movie he is going to have the same outcome every time. It's a reading of a set outcome of events. He might kill them all or only take out half of them before being stopped, but whatever happens the course of events is fixed and will happen every single time you watch that movie or read that book. What matters is what type of story it is. It could be a drama, horror, sci-fi, etc, etcWith games that isn't the case. Every time you try it you'll get a different outcome (assuming it's gameplay and not a cutscene) and the primary concern is how you interact with it. a FPS where you directly shoot people in the face is different from a Turn-based strategy where you carefully guide Dirk McShooty around which is different from an interactive text-based adventure where you type "GO NORTH", "SHOOT TERRORIST".With Movies and books the method of engagement is set. You look at them with your eyes and for movies listen with your ears. With games it can vary incredibly. You might circle strafe people and shoot them in the head, it could be a patient strategic exercise of moving your character, etc, etc. It all depends on the genre.Not only that, but being honest for a minute, even games which have a narrative have one which is very poor. Although there are some highlights ranging from the Walking Dead to The Last of Us to Undertale, these are a minority. For each of those you have dozens of Duke Nukems, not to mention several Fifas, where the narrative and emotional investment is paper thin or non-existent. The same interaction between media and person simply dosn't inherently exist when it comes to games.Movies and books focus on the type of narrative because narrative is inherently central to books and movies. With games that is not the case. Although it is possible for games to have a strong narrative, as with Spec Ops, they mostly do not have one and focus on gameplay. even then when games do have a strong narrative, the method in which players interact - the type of gameplay - is still a central function. No matter how good the setting to Alpha Centurai is, people who don't like TBS will hate it.Games that evoke emotionThis is a very minority type of game and the example you give in fact is even classifies itself as a non-game so I can't really count it as an example seeing as it specifically tries to present itself as not a game. But even assuming that there is a point to be made that perhaps this small minority of (non)-games can't be explained in terms of genre, this doesn't apply to the vast majority of games. For every arty farty story game, there are two dozen where you blow the heads off aliens with shotguns for poorly explained reasons. If the vast majority of games should still be explained in terms of genre, then the debate issue of Video game genres shouldn't be defined by mechanics, controls, or intended "ways to play the game" falls in my favour because a large proportion of them SHOULD be defined in those terms.