Massive generalization of how you feel about games. So many people on this site confuse how they feel and try to generalize that to how everyone feels. There is NO catch all in this case. Some people find the gameplay to be the most important thing. Some people find gameplay to be most important and some people enjoy the atmosphere more. I need both. But that's just me.

Your argument didn't prove that gameplay is most important in all games, being necessary doesn't make it the most important part. 

He's talking about how the whole experience makes him feel and you said he was wrong and used the definition of video game as the argument when that wasn't what his topic was about.

I think I get where you're heading, there seems to be two different debates going on.

First, one debate around the importance of gameplay in a video game which in my opinion can be summed up this way:

A game with bad graphics can still be enjoyable
A game with bad music can still be enjoyable
A game with bad story can still be enjoyable
A game with bad gameplay is not enjoyable (I did say bad gameplay, not limited or simple gameplay) which makes gameplay essential. The one component you can't screw up.

But that's not exactly what bananaking was talking about. He was arguing that gameplay doesn't have to be the central aspect of a game for it to be great, that minimal gameplay can yield a great result if the experience moves you. On that front, I agree with him, deep and rewarding gameplay is not required in every game. Just like a complex and engaging story isn't required in every game.

Why do you think that's mutually exclusive? I get totally immersed in Minecraft too, just as much as in Dear Esther. However fighting and sports games don't interest me at all, can't get immersed in that. (Except racing games, can't get enough of those)

Good gameplay alone can't carry a game for me. Spelunky is rather boring to me.
I can forgive bad gameplay if the rest is great. Ico's gameplay, beat the same couple monsters over and over, very annoying. Still my 3rd favorite game of all time.

It comes down to why you play games. For me, it's getting immersed in a virtual world. For others it might be a test of skills, which would put gameplay first. I don't play games to boost my ego, again except racing games, I'm pretty good at them :), I play games to experience new things.
I'm going to continue my tour to Sagittarius A now in Elite Dangerous. Lacking greatly in the gameplay department, yet being immersed in a journey to explore the center of the Galaxy is great.

But it's the pointing 'n' clicking that lets you interact with the environment, and in turn, immerses you in the world.

There was even a third debate going on about games not being games without gameplay when that's not the topic at all.

As for your fist summary, I have actually experience a few games where though the gameplay was bad I still had fun. The Rayman Raving Rabbids games on the wii had bad gameplay, but since it's a party game of mini games my family still had a blast playing them.  Could I play those games for long periods of time? If I had to the wii mote would go through the TV, but on those occasions with family they were great. Would I play them on my own? No but there are even many games with great gameplay that I can't play on my own because they are better in groups.

Also as I mentioned before, the gameplay of some games looking back is terrible now but at the time with no better options so while they could be enjoyed in the ignorace of better gameplay are now unplayable.

Freaking Golden Eye on the 64! I remember firing it up one night a few years ago with some friends and was like "Oh man, this is gonna be like the old days!" and I see how unplayable and godawful the game is now. STILL though, slapper only and sliding down for the entire death match is enjoyable all by itself! So just reinforcing your point on a game having bad gameplay (controls/movement, etc.) but still being fun on different merits.