It is a myth that all of Oahu is a concrete jungle. The best beach I visit in Hawaii is Kailua (where Obama goes each Christmas - and he's Hawaiian). Windward Oahu in my opinion is the most beautiful part of Hawaii - and it's a one hour drive from Waikiki.
I totally agree about the comment on Windward Oahu. It has a very Polynesian feel at certain stretches. There are several gorgeous beaches dotted the drive all the way up to North Shore.
We certainly do not rate Oahu below all other islands.
We like Oahu which has its attractions of diversity. Maui and Kauai are on par with each other though their charms are quite different.
Hawaii is the least favorite island to us. We did a return visit this past March and were utterly disappointed, including the Sheraton property.