There really aren't many things that truly compare to an open road or a track day. The feeling of a machine between your legs (get your heads out of the gutter!).... It's such a sense of freedom. If I ever were having a bad day, I could just ride and all my worries would work themselves out. Plus, the motorcycle community is like none other I have ever experienced. You wave to other motorcyclists on the road - regardless of type of bike. You don't get that with cars. Cars are all import vs domestic, FWD vs RWD, N/A vs forced induction.... A bike is a bike and the human on that bike is good. End of story. Once you become a motorcyclist you are forever a motorcyclist. It changes the way you look at other cars, driving, safety, friends/family.... everything.
The closest thing I can think of that might compare to the sheer thrills of a bike would be an orgasm or getting to ride shotgun with a pro drifter (Vaughn Gittin Jr) at Irwindale. lol But yeah, not much compares to the complexity of emotions and experiences a bike can offer.