certainly voting for the original.
It was great when i first played it and quite frankly i still love it.
Had some pretty neat areas, a likeable battle system, good visually, good music wise(by gba audio standards anyway), wasnt unbelievably broken, and good use of mario bros moves(unlike the others which didnt even use them).
Only things i didnt care for was the whole bossing around. It seemed like someone always ordered the bros around which was kinda meh, also the lack of difficulty, but otherwise, it's a great game.