"Every customer a custom" is the motto for 2010. And at the top of the lineup is the Electra Glide Ultra Limited; Harley's best-selling model '09 (in spite of its $25K price tag)
So in 2009 that was the top selling model......I'd have to say overall seller of all time would have to be the sportie because it has been around and never dropped since the 1950's.
I think that sportsters are the best selling model due to the price being significantly lower than the other models. They also appeal to the younger riders who want to step up from the metrics.