I overshadowed Jack Frost with Pyro Jack. I loved having Pyro around he helped me in battle so much in P3. Funny thing is, while I thought I was over leveling Pyro Jack I was actually evenly leveling both Jack Brothers. I really just used those two through out the game, I didn't use King Frost nor Black Frost.
I believe that both of them are extremely popular. If you compare the love megaten fans give to Jack Frost with the love given to Pyro Jack indeed it's not that much, but then again, what about the less popular Loki, Samael or Dionysus? They are usually strong with awesome skills, they got elegant designs yet in comparison to Jack Bros they don't even have half of the fans.
Everything has to do with advertising and marketing. That's why frost and pyro are so popular while ripper is unknown. Because they have became mascot characters and exist in every megaten (and non-megaten titles too). Also I think that Uriel is pretty popular.