Why in this RPG's, the villain generally is cool while the MC is extremely boring?
Seriously. You have Wiches and Deathknights as villains on JRPG's while the protagonist is rarely even non human and non swordsman.
I have very little experience with JRPGs, but in both I've played (DQ8 and 11) the idea seems to be that the main character is kind of a blank slate for you to RP as. They don't even speak in either game. A lot of the team members and other characters can be very likeable and cool though.
As for withches and deathknights, I don't think they'd be particularly interesting playable characters either, but if they were available, they'd likely be just as plain and silent as the main character already is.