Definitely depends on the kid!
My daughter has been at 5, 8 and 9 and still hasn't ridden Dinosaur or TOT. Big Thunder was one of the first rides on her first trip when she was 5, but it scared her so we never pushed anything further on that trip (she had ridden similar roller coasters at local parks tons of times, so we were surprised by the reaction). She had started to like rides with drops by the time of her 8 year old trip and she insisted she wanted to ride TOT, but she got to the loading area and had a breakdown and had to get out of line. She just mentally freaked herself out. I think she might have ridden it this most recent trip at 9, but we didn't even try. We knew Dinosaur would be bad for her, so we've never even tried it. She does love Seven Dwarves, Splash Mountain, Everest, etc.