Good Japanese Food on Oahu/Honolulu, but really touristy. But good if you like shopping or being around a lot of people/where the action is. If you want to relax, be secluded, and be one with Nature, Kauai. Golf and nice resorts on Maui. Adventure stuff on Big Island (and lava lol).
I lived in Maui for a few months and visited the big Island of Hawaii. Maui is the greenest and most expensive, Hawaii is the largest (I think) and also nice to visit though the island is like split into 2 (one part looks like Mars and the other like any beach destination). Oahu is the only Island with a highway (which doesn't go anywhere!) but can be interesting too. All in all, I'd say either Maui or Hawaii but I may be biased 🙂