well out of rollercoasters at disney i would say that rock n rollercoaster starring aerosmith is the best.
it launches you from 0-60 mph in just 2.8 seconds. and then goes upsidedown straight away.
and it has awesome neon signs and aerosmith music playing.
then i would say splash mountain is the next best. it tells the story of brer fox trying to kill brer rabbit. and has catchy music and awesome animotronics through out the entire ride. and it plunges 87 feet in to a "brier patch". and you get a bit wet.
then space mountain. it is indoors and in the dark. its pretty fast and its hard to tell where you are going. so even small drops give you that awesome feeling in your stomach.
ok now for the best thrill rides that aren't rollercoasters.
tower of terror is the best. you go into an elevator that goes directly to the twilight zone. you see what happened a group of 5 people on a dark and stormy night a long time ago. then you get to experience it for your self by free falling multiple times while in the elevator. it is sooooo amazing!
then there is mission space. you are on a mission to mars. the blast of feels sooo real. and you feel g-forces. you just have to go on it to understand how cool it really is.
test track is like a GM testing facility. you get into a convertable car and go through the "tests" that all gm cars must go through.
you experience bumps, break testing, hairpin turns, hot, cold, and evassive manuvers. and then you do the car running into the brick wall test. and you go outside on their track and take some curves then reach 65mph. its great!
been to disney world 44 times since 1986