I haven't been to every island so some of this is second hand from my friend Sandra's husband Andy.
  1. Oahu
    The most developed. Think Waikiki. The most tourists so most awesome food options. Get shave ice and fish tacos and stuff with macadamia nuts. You can get away from the most touristy areas by driving around the island.
  2. Big Island
    Least developed, with a striking alien-like landscape. Hilton resort is awesome with dolphin pools for kids, etc.
  3. Kauai
    Oldest and most lush (think Jurassic Park). Try powered hanggliding or helicopter or scuba here. Hiking also great.
  4. Maui
    Big resorts. Good for luxurious relaxing. Developed somewhere in between Kauai and Oahu. More expensive than Kauai.
  5. Overall: Kauai and Maui. If mostly going to chill and relax at a resort, Big Island. For food, Oahu.
  6. Other: Na Pali coast. Sunset dinner at Beach House. Ahi Tuna Burger at Polynesian Cafe. Swimming at Queen's Bath.