Then clearly you don't know what the one and only definition of gameplay is. Just because the story in Super Mario tends to be separated from the gameplay you can't use that one example to dismiss all prominent examples where the opposite is the case.

You don't play The Walking Dead simply by making mindless decisions. You play it by following the story, putting yourself in the characters' position, analysing the situation and then picking the preferred option that is available to you. To throw all the rest away and claim that only that last part can be considered gameplay is absurd. Like I said before, it is just as absurd as the claim that the way you play cards is by moving your hands around. In both these cases, the thinking process is the core of the gameplay.

I'd say all games have to have some sort of interaction method, so "gameplay" is the heart of every games, even point and click adventures... or QTE fests like Heavy Rain...

However, story, ambiance, etc. can raise it further, a game with poor writing and/or acting like Castevania:SOTN or Thomb Raider 2013 can still be considered great, even if people find the story/acting laughably bad... I took two games I liked to different degrees, Castelvania:SOTN is one of my favourite games of all times! yet the story is cringe worty, however the ambiance is amazing!

I guess the answer is, there is no right answer, there are many different type of games, different type of gamers, different developpers and tastes change over time... so to each his own, I don't like heavy rain or the point and click adventures type games, but many people do... just accept it and let them have what they want, it's not as if it robbed others of their games...

I'd personally consider text a graphic (and would never play an Infocom for the gameplay lol), but for the sake of simplicity let's just say 'visuals'. A video game without visuals is not a video game. Does the necessity of visuals mean it should be a primary focus for every game? Of course not. As long as the visuals do a good enough job of presenting the experience, it's fine for a game to put more weight in other things. The same applies to gameplay.

Heavy Rain is a particularly good example of this. Much of its gameplay is very rudimentary, but is good enough that it can present the story without bringing attention to itself (the story being the key reason most people play it). As long as you can hit that 'good enough' mark with anything, gameplay included, you can focus on other things. I'd agree with anyone that said having a solid interactive foundation should be the highest initial priority (regardless to how bareboned), but it being the overall focus is optional.

Heck, one of my all time favorite games (Steins;Gate) has literally no gameplay other than making story choices, yet i enjoyed it more than almost every gameplay focused title out there. Does the inclusion of choice make me enjoy it more than if it were a book? Yep. Is it the reason i'm enjoying it? Nope, that would be the story and characters. That i or anyone else is able to say "i'm playing this for the [not gameplay]" is all the proof i personally need that a focus on gameplay isn't inherently necessary, despite the necessity of its basic presence.

That all said, i would agree that gameplay is more frequently the "most important thing in games" than anything else. I just don't believe  it's a universal truth.

Just working doesn't make gameplay good. The gameplay isn't the draw of those games. Nobody is buying Journey going "thank god, I've always wanted a walking simulator!".

The gameplay takes a back seat in games like The Walking Dead. The gameplay is there mostly because it needs to be. Does that stop those types of games from being great? Of course not, because gameplay doesn't always need to be the most important part.

I'm glad that many fans find comfort and joy in the stories and emotional weight of video games. I do too. But, for me, interesting stories, characters, and locations are virtually meaningless without a strong mechanical foundation underpinning them. If a game plays poorly, no amount of professional voice acting, clever writing, or spectacular graphics can salvage it.

When I watch a movie or read a book, I look forward to interesting writing, impressive production design, and artful composition. When I play a game, whether it's Apples to Apples or basketball or Contra, I expect a different set of features. I expect a set of rules, and a set of goals, and the opportunity for me as a player to navigate those rules and reach those goals according to my own strategy. Therein lies the joy of games, at least to me. 

Interactivity is part of the gameplay. It's like saying the most important part of street racing isn't the car, it's the engine. The engine is part of the car, just like interactivity is part of the gameplay.

Well put. Additionally, a medium without gameplay cannot be considered video-game. However, if a medium contains gameplay and no trace of storytelling whatsoever, it can still be considered a videogame.

I agree, but i don't think it means gameplay is immediately the most important part of any game. It more frequently is than anything else, but it's not universal.

Quoting one of my other posts "There's no denying that having a solid interactive base for your title is vital (regardless to how bareboned), but it doesn't have to be the focus." Once that gameplay foundation is built, the focus can be moved to other things. If those 'things' are the reason people enjoy the game, i'd consider them the most important part.

No, some people physically become ill from movies, and cannot keep watching. Some people become do dad they cannot watch anymore. Strong emotional responses aren't choices. 

Though I'm not sure where this tangent relates to importance or not of gameplay.

The point that I was making before was just how the level off challenge is independent of gameplay and has it's own influence to the value of a game. too easy, too hard or no flexibility at all when it could use it

And the bolded says it. take away the gameplay, and it transform into something different, not a game. But more importantly, have bad gameplay, and the game is ruined. You say Steins;Gate practically has no gameplay, but it does have one and it works. If the gameplay wouldn't work, the game wouldn't be good, besides story, visuals and whatever. You dismiss this too easily because the gameplay seem simplicistic in your view. But the point is, even simplicistic gameplay can be good. And complicated gameplay can be bad (actually it often is). So my point stays: gameplay plays an integral role. And while the other components are not essential, they still can have heavy impact on the general quality, but while a good game without good sound/graphic/story can exist, a game without at least basically working gameplay never is good.