We just got back from a trip with a 4 year old. He loved all the rides and said Everest, Space Mountain, and Tower of Terror were his favorites. He was a little nervous the first time on Dinosaur, but then happily rode it several more times. He loved It's Tough to be a Bug at three, but this trip he was scared by it. Probably the only thing that really upset him and we didn't see it coming since he really liked it last year. So it really just varies by kid. You know yours best, but I usually recommend starting slow and building up to bigger, scarier rides.