Awesome remake of the fantastic game!
Still, that shouldn't turn you away from this game. It introduced many Mario characters we know today like ShyGuy. It was also the first Mario game where you could play as Toad and the princess as well as Mario and Luigi.
Not much has changed except for graphical improvements, some more enemies and some new bosses. It still has the same music and game play. Unlike other Mario platformers, this isn't about getting to the finish quickly. There's no timer. Instead, you find your way (a lot like the Zelda games) to the boss, kicking-in enemies as you go.
It takes a while to complete the levels but there are only about 27 They are guaranteed to keep you playing unless you're a Mario master that can complete any Mario game in 2 secs max. It doesn't have much replay value to it, but when you're on a journey, it's fun to turn on your GBA and play those levels again.