I agree with everyone talking about the smells you experience on a motorbike!
When I went out for my first long ride through real scenery last weekend, I was amazed at the different aromas of grass, trees, mud (!), fires burning, etc etc...it really heightened the experience of being where I was. Plus you're right there in the middle of the elements, which feels amazing - I rode through rain, wind, sunshine, the lot, and it felt pretty incredible to be so at the mercy of all those things.
4x4s are good..but for me, at the moment, bikes are better!