It's equality of opportunity that I personally consider most important -- that everyone has the opportunity for their hard work, study, and application of knowledge and effort to be put to good use. What race you are, what color your skin is, what gender you are, what your sexual preference is...none of these things should keep you from having the same opportunity to succeed as anyone else.
Things are certainly better in that regard than they were 10, 20, or 40 years ago -- but there are still considerable barrier and fairly widespread prejudice. For example, I'm a white guy married to a Filipina -- and just a few months ago, while in a grocery store shopping with my wife, some bigoted white woman out of the blue passed by us and said to me that I should be associating with my "own kind"...and that in "liberal" California.
Give it another 20-30 years for the super-bigoted generation to die out, and I think it'll be even better. Bigotry learned from birth is hard to overcome, but the younger generations are less hung up about race, color, sex, and gender than the older generations are.