We've been to the 4 major Islands and like them all. Our favorite for "things to do" is probably Maui.
1.Haleakala Volcano
2.Road to Hana
3.Great golf
4.Molokini for snorkeling
5.Great restaurants
6.Lots of shopping
We like the Big Island for the diversity of landscape. Tough to pick just one but if I had to pick one for a 2 day trip I'd pick Maui. ENJOY.
Phil