I agree with Nels,
Choppers are another whole world to explore! And at least when I was in the Corps, learning to fly choppers, was like going to a pilot's graduate school.
We had already gotten our wings. Then we had to learn another totally different form of flying. A hover, side-slip, and even flying backwards were all alien to what we had learned. And what you have learned as a fixed wing sim pilot as well. And yes, those actions are all controlled by you, not an autopilot.
Even if you only "fly" fixed wings there are so many different landing areas all over the world to explore. High altitude, short field, water landing, IFR weather, etc. Not to mention a ton of different aircraft to learn.
I also enjoy flying to airports I hear about on the news or read about in travel brochures and especially Flying magazine. As well as destinations I've visited throughout the world. How about a flight around the world in a small aircraft?? That challenge will take a ton of planning for such things as planning fuel stops etc. if you do it accurately with failures enabled!!