favorite area is the Mauna Kea resort area. Stay at the Mauna Kea, or the Westin Hapuna Beach. The are lots of vacation rentals and homes in the resort as well. It's all part of the same resort complex so you can go to both hotels, beaches, and restaurants.Those 2 beaches (Hapuna and Mauna Kea) are the best in the state IMO in terms of water clarity, waves, sand, snorkeling, crowds, etc. Plenty of other things to do there and on the island: golf, hiking, snorkeling, site seeing, food, volcano, etc. You can do tropical rainforests, desert, mountains, black sand beaches, green sand beaches, lava flows, and everything in-between.
I've been to every other island (although I've never stayed overnight on Lanai), and Big Island is the one for me. Maui and Kauai are great, and Oahu is ok for a couple of days. But I go to Big Island every time I go to Hawaii.