For steak, I'm at Morton's, Hy's, and Wolfgang's regularly on Oahu, but if it helps, the best steak I've had on Oahu for quite some time was, surprisingly, at an Italian restaurant in Waikiki two weeks ago called Il Lupino. They had an amazing striploin prepared in the Italian "Tagliata di Manzo" style. Turns out the owner is also the owner of Wolfgang's steak house, and the steaks come from the same supplier, which might be one of the reasons it was so good. Don't know about the rest of the menu however.
Note it's very much a place catering to tourists, if that makes any difference.