For example, rollercoasters mean that life has significant ups and downs, twisting and turning all the time. Roller coasters are also the most cliche ride to use, so I can't really generalize very well about people who use that particular metaphor.
Someone who says that life is like a ferris wheel thinks that life just goes in circles, or more likely, cycles, and never actually gets anywhere. These people have an air of wisdom because they learn the patterns and predict what will happen. Unfortunately, they give up on things too easily for my tastes.
Someone who compares life to bumper cars puts themselves in charge of their own happiness. This kind of person tends to be more assertive, and sometimes to trample other people's desire for happiness in the pursuit of their own.
Then there are the people who don't choose a single attraction, but instead decide life is the entire park. They are more likely to try to do everything. After all, they already paid to get in; why not make the most of it.
Merry-go-round people see life as aimless (as do the ferris wheel people), but they also would view it as artificial. They more superficially interact with people, with the "my horse is prettier than your horse" attitude.
There are even a few select people who see the other people as the main attraction. Value other's experiences or the memories brought up by those experiences more than they value their own present. They are the ones who like to see the excited faces of the children. They smile when they hear the screams from atop the roller coaster. They aren't participants in the action, or are they? They are the gentlemen you always see sitting on the bench. They are the ladies who throw a ball at a bottle, then turn to hand their prize to the nearest child. They bring constancy to the experiences of all the others.
What attraction do you see your life most as? Write and tell me.