Early last summer, I was afraid that the thrill riding days of my youth were a thing of the past. My wife will not ride many of them (combination of fear and bad back issues); our older daughter was rarely available when we visited the local amusement park -- even though it is right in our town, she had crazy work hours and a life of her own. Our younger daughter was scared silly of all the coasters and had a COMPLETE meltdown when we coaxed her onto the minor small roller coasters.
But then she came around. Big sister was able to come once or twice and got her back onto the small ones and she decided that after you get past the nervousness, they were actually quite fun! Then in late July, some friends from Boston came to the park for a weekend and she HAD to be brave since they had a son who was just a year older than her and he was determined to ride them all! Slowly over that weekend, she rode each of the bigger and bigger coasters - each time afraid, but willing to try it ONCE... There were a couple that she was still too afraid to ride (300 and 400 feet tall!) and the friends' son also decided that they were too tall for him as well.
About a week after they left, she and I rode the last two together (my very first time also on the 400' ride). So now I have created a monster and my thrill riding days have been extended for at least as long as young daughter is home and capable of riding!
I am absolutely terrified of the ferris wheel and the bucket sky ride types, but put me on a speeding coaster and I have a blast. I am lucky to live five minutes away from the best amusement park in the world in Sandusky, Ohio and the best ride in the park (and to finally answer the original question) my favorite is still Millennium Force!