For me it would have to be the challenge, (the pursuit..which probably ties into the challenge) and the love of nature. Nothing beats seeing all the beautiful sunrises and sunsets, seeing the critters come alive, and all the other things animals do that you can't always see on the nature channel. The pride and joy you have over a kill usually takes a back seat to everything else (unless it was a wiley pheasant that my dog tracked and tracked and tracked and I was able to harvest....but then again the kill takes a back seat to my dog's great performance. In this situation, the kill was more for the dog's enjoyment/reward than my own.) Just my $.02

EDIT: Another thing I really love is that I can get away from everything and put my troubles behind me while hunting....there's just something soothing about that.