Mario is Missing will always have a special place in my heart. I was pretty lousy at games as a kid, and I also liked Luigi a lot more than Mario. Then one day at the game rental place that we often frequented, we found a game starring Luigi. That and the fact that I could play it, and that it helped me out a couple times when playing along with Jeopardy, were enough to make me rent it probably upwards of twenty times, until I finally beat it on the day it was due back that twenty-somethingth time. And one day while we were there to pick it up again, we found Mario RPG, my mom and I got hooked on it, and we went out and bought it soon afterward. I have a hard time going back to Mario is Missing now, but I'll never abandon it. And yes, the music is awesome.
I wish someone would make a sequel to Mario is Missing that was more of an actual game. It could still have the quiz questions and stuff, but with actual levels. And more emphasis on the "figuring out where you are so you can send Yoshi there" element, with a lot more difficulty to it.