I went on my first trail ride a few weeks ago, as you read, and even though I had a difficult horse, I had a great time! We went again last week, I on a different horse, and I had an even better time!
We have trails around here that go threw woods and open grasslands, I have even seen fields that have been groomed for horse trails. It's hard to say which is the most popular between the eventing, western gaming, jumping and trail riding etc.
I know that once I buy my first horse, I will be using him/her for mostly trail riding. I know that when I'm riding, either it be in an arena, or on the trail, my worries melt away for that time being, and I can think of nothing else but being on the horse, and feeling it move beneath me. It's safe to say that's why a lot of people ride, to get that feeling.