Ah, I see your point now...Nice post, but I still disagree.
For one, the punishing in Brawl not being big...Are you serious? An Ftilt from Snake is 21%, that's devastating to MK. His grab game can lead to 48% with just 2 grabs if you predict wrong just ONCE. DDD's grab does 16% with every throw, and his other throws can be tech chased for more damage. MK gets punished just fine.
Also, your last statement is very interesting, and almost makes me want to contradict myself, but again I disagree. First off, it's a fact that player skill>character selection. That means, if you win with Snake on your first match and you are a better player, chances are you will win on the counterpick...And even if the counterpick is TERRIBLE and you ARE terrible on that stage and you just are forced to switch to MK or else you have no chance...Well, then you switch to MK.
This only seems bad because, underneath the surface, makes it look like MK is necessary to win no matter what. But a deeper look just shows that it's nothing more than CP'ing the best character in the game. Look at Ken, who secondaried Fox for his troubles with Sheik. (Not to mention, Marth vs Sheik is hard for Marth and he loses pretty badly, but since Ken is good he managed to beat Sheik with Marth, just like good people can beat MK with matchups as bad as 60-40) ANYWAYS...Azen plays so many characters in both games, to CP with. Every Marth main secondaries Fox. It's just how it is...Why don't they main Fox though? I mean, surely they want to win their hardest and by playing Marth they are obviously lowering their chances of winning and being less competitive right? Wrong.
It's called player preference. People realize that MK is NOT unbeatable, and therefore it doesn't matter if he is the best character or not...He can be beaten by other characters, and they prove it. That's what's GOOD about Brawl, is the fact that there are indeed several characters that do well vs Metaknight, and even if people don't realize it, the game is diverse in the fact that Snake, Lucario, Olimar, and to a lesser extent Diddy, Marth, Kirby, DK, ZSS can all deal with MK just fine. Azen, Bum, Snakeee, Chillin/DSF/Ally/Afro, Chu, Neo and Roy R all show that MK is beatable by other characters.
I'm sure if these players really really thought MK was unbeatable, at least a few would be playing him since they want to win so bad...But since they realize he's not unbeatable, they can just win with characters they like. It just takes a ton of work, and a lot of people don't want to put in that work, so they don't realize it.