I doubt it, you really cannot customize much on OS X like how you could with windows xp. The most you can nowadays do is icons. Window designs are rare and hard to find with system file edits. With the release of Mountain Lion, there isn't anyway to change the dock even. And yes OS X apps have some best designed icons ever. You should see the attention to detail. Just checkout dribbble.com. The same can be said for iOS icons. OS X is meant to have neutral colors to the eyes and let the user work.
The problems in the design of OS X are small cosmetic issues with certain applications such as the linen, the leather used for calendar and address book. Hopefully this ugliness will be removed soon.
Well while it may not be possible in the latest versions, during vista and the early 7 days, they where rescinding everything in OSX, I recall dark resins where particularly popular but there was a lot of reskinning going on with OSX. And today a lot of people are reskinning to drop the skeuomorphism.
And after all, windows has more built in customization abilities from the get go with users abilities to change the colors of their windows.
As for icons, that's p to the app designers themselves. There re many windows apps with icons that rival or even beat Mac icons, but of course when your app universe is 100 times bigger, there's going to be a larger amount of ugly apps/icons.
Windows users also tend to be more focused on the app working no working good/effectively, whereas an apple users will pick the pretty app over the working app. The App Store shows this effect a lot. Personally, I wish I could have both, I wish my mirc could have the function of mirc with the mdi windows, or a tileable interface with the looks of one of the nice new metro irc clients.
That's being quite cheeky... just sayin'.
Cheeky doesn't make it untrue