For me, it's all about equality.
I first found Diana on a magazine shelf back in the early 70s. At that point in time, female role models were few and far between. I'd been lucky enough to stumble onto Emma Peel on PBS, but for the most part, female roles were generally limited to girlfriends and victims.
So there I was, staring at a comic book with a woman on the cover and her name across the top. Next to it was a Justice League where she *and* Black Canary were literally standing shoulder-to-shoulder with Superman and Batman. For me, this was amazing! I was hooked.
At the time, women couldn't get a credit card without their husband's signature, and girl's couldn't play in little league baseball, although my sister was one of, if not the first to do so (she played before there was a lawsuit to allow girl's to play - I want to say 1972).
Diana showed me that a girl could be just as strong, just as respected and just as competent as the men. Women were equals in comics and Wonder Woman, to me, was at the forefront. A couple of years later, I got to see Wonder Woman fight Superman to a standstill, proving that women can be powerhouses as well.
It's why I'm always vocal about Wonder Woman remaining on an alpha level of power - she's the shining light for my generation; an example of equality at the highest level of super-humanity.
And she did it with love and compassion. She could be powerful and still be feminine and still be accepted and respected by the male heroes that dominated the industry.