I always liked the Road King since it first came out as the Electra Glide Sport (or the original Duo-Glide if you prefer), to me it's the original classic motorcyle style, the kind of look that never goes out of fashion. It's not influenced by wind tunnels or the B1 Bomber it's just an old school bike with modern features: cruise control, abs etc.
Just traded this an 09 RK that had 62k miles.
The Electra Glide follows the same philosophy and it's really the same bike as the RK with the "Batwing" fairing thats been available since 1969. Like the RK it's modern in many ways, ABS, cruise control, heated grips, AM/FM/CD etc.
My new bike 2011 Electra Glide Ultra Limited
I'm not sure HD fits into retro style since some of the styling cues haven't changed all that much in 40 years.