MK's NOT overpowered. -_-
Yes, he does win every match-up in the game (Pikachu is actually considered even), but he has plenty of near even match-ups that are definitely winnable. MK was banned for a little bit cause of the URC, but the URC was disbanded (because pretty much everyone who doesn't suck hated the MK ban) so MK is legal again. I'll agree Meta Knight is broken on stages like Rainbow Cruise and Brinstar, but with the Apex Stagelist (Battlefield, Final Destination, Smashville, Yoshi's Island, Lylat Cruise, Pokemon Stadium 1, Delfino Plaza, Castle Siege, Frigate Orpheon and Halberd) Meta Knight is not broken. He still needs to outplay his opponent to win the match-up (unless it's someone who has a terrible match-up vs MK).
The Japanese only play with FD, Battlefield and Smashville (unless they're preparing for international tournaments) and they're considered the best in the world right now because two of their players took both of the top 2 spots at Apex 2012. Meta Knight also rarely wins tournaments in Japan, it's usually Nietono (an Olimar main) or 9B (an Ice Climbers main). Sometimes Otori and RAIN (MK mains) do win, but it's usually Nietono and 9B.