Hmm...
I don't think Otoya should count.
Though he is a smooth talker...ten outta nine always had him fail when it comes to the Ladies.
That being said, the best Womanizing rider isn't Human, but rather an Imajin.
Now...it can be argued that Urataros succeeds in stringing along the ladies coz of Ryotaro's looks, but let's remember this: Ryotaro by himself is a wuss..and the only lady whose heart he won over on his own is Nee-san's.