OK, I left Hawaii about two weeks ago. I dived with Lahaina Divers at their Hammerhead location, Carthaginian, and the wharf. Saw hammerheads with them as well as a big school of spinner dolphins while diving, which were both fantastic.
I dived with Seasport Divers at Niihau. Seeing monk seals underwater, and lots of Sandbar Sharks was wonderful. But I was unimpressed with the fact that, spending $400+ for a day's diving with them, the "large lunch" they promise on their website turned out to be just cold pasta and pre-sliced bread, cheese and ham, and water to drink.
Anyway I do feel that the diving was comparable to that in Indonesia or the Philippines. Most of the fish that I saw in Hawaii could be seen there as well. It was good to see a number of endemics, and I really liked the concentrations of butterflyfish off the drop-offs, which was something new to me, but otherwise there were a lot of similarities. Not sure why everyone on this forum has insisted they are so different, unless they are referring to the standard of catering on the dive boats (!), which frankly would have been a lot better in Indonesia or the Philippines.
Here's a list of fish I have been able to identify (+ indicates a Hawaiian endemic). The numbers were really good, but most could be seen widely across the Indo-Pacific.
Arc-eye Hawkfish
Bandit Angelfish+
Blacklip Butterflyfish
Blacktail Snapper
Blue-striped Snapper
Bluefin Trevally
Bluespine Unicornfish
Bluespotted Cornetfish
Bluestripe Butterflyfish+
Bluestriped Snapper
Brassy Drummer
Dark Surgeonfish
Fourspot Butterflyfish
Freckled Hawkfish
Goldring Surgeonfish+
Great Barracuda
Hawaiian Chub+
Hawaiian Dascyllus+
Hawaiian Flagtail+
Hawaiian Hogfish+
Hawaiian Sergeant Major+
Hawaiian Spotted Toby+
Hawaiian Spotted Toby
Highfin Chub
Humpnose Bigeye Bream
Indo-pacific Sergeant Major
Island Goatfish
Lei Triggerfish
Mackerel Scad
Manybar Goatfish
Milletseed Butterflyfish+
Orangeblotch Surgeonfish
Pacific Bronze Chromis
Pacific Orangespine Unicornfish
Pacific Sailfin Tang
Pebbled Butterflyfish
Pinktail Triggerfish
Pyramid Butterflyfish
Raccoon Butteflyfish
Redfin Butterflyfish
Redlip Parrotfish
Rockmover Wrasse
Saddle Butterflyfish
Saddle Wrasse+
Sandbar Shark
Scalloped Hammerhead
Schooling Bannerfish
Smalltooth Jobfish
Surge Wrasse
Threadfin Butterflyfish
Undulated Moray
White-tipped Reef Shark
Whitebar Surgeonfish
Whitemargin Unicornfish
Whitemouth Moray
Yellow Tang
Yellowfin Goatfish
Yellowfin Surgeonfish
Yellowmargin Moray
Yellowstripe Goatfish
Yellowtail Coris