I don't have to explain anything. I show the game/vids to people and they are amazed. If they want to get into it they will eventually play it and get stucked (it has actually happened). Otherwise they don't play but what's the matter? I don't think it is necessary toinvolve people who aren't genuinly interested in the game.
There's nothing to explain really. We just play these games because we enjoy playing them pure and simple. Like most I'm attracked to the game because of the challenge. People who play seriously and frequently will eventually get better given enough time. I'm certain we'll have a lot more extremely skilled Western players in a few years. Friends who have seen me playing think I'm amazing, but I'm quick to show them videos of the truly amazing people. I was once told there were more useful things to spend my time on. Truth is that everyone is doing at least a few things that would be considered time wasting by others. So I don't care about that.
I usually don't explain why I play TGM so much. I usually go with "Yup, that's actually human. Lot of training, but human.". But then I study in one of the most geeky place in the planet (EPFL), so having an elite Tetris player is not a surprise amongst those mad scientists . But if I wanted to explain it in details, it would have the following points: Tetris is elegant. "Easy to learn, hard to master" as they say. Tetris (and most of TGM clones) doesn't require an hepta-core-from-the-computing-hell to run, so I can play it wherever I like. Tetris has a near-infinity replayability (2x10^60 possible playfield, more than the number of oxygen atom in the whole universe). TGM makes Tetris more elegant and prevent it from being boring. TGM is never unfair, or at least tries to(*): it has an unpredictable yet regular randomizer, consistent and logical rotations(**) and there is no brusque acceleration that would takes the player by surprise nor unsurmountable wall that would kill an unaware beginner. There's a grading system that gives a very paplable ranking amongst the players ("I'm S4" is infinitely more intuitive than "I finished the 1st section in less than fifty seconds), effectively giving them the will to continue and improve. Reaching a new grade is a very, very satisfying feeling. Warning: may sound even more geeky than intended. Tetris enables me to enter into flow state / "the zone". That's not my only way to enter it (I felt it in karate, iaido (!) and I'm pretty sure by doing some hard song in Guitar Hero), but that is nonetheless an pleasurable feeling. (*) Murphy's axiom of Tetris: you will never ever get the right piece at the right moment (**) well, at least on the wallkick part ; SRS' center-of-mass rotations is logical after all.