[.`JenJen`.]
But I guess H.O.T wasn`t successful?
H.O.T were INCREDIBLY successful. The only difference really is that it was "harder" to become more internationally known, since mp3 downloading wasn't as wide spread then as it is now. So now, you have people from America, Europe, Australia, etc, buying albums of artists that don't exist in their country, all because you've heard the music on the internet.
I'm not sure why H.O.T broke up, but they all went on to do their own things - Kangta and Moon Hee Jun are successful solo artists, Woohyuk and Tony Ahn and Jae Won (I think) formed JLT (jtl ..? i can never remember which way it is) and then of course moved onto solo projects of their own.
They were and still are successful.
Super Junior are just new and fresh, and have the internet to help spread their music and gain more international fans. I don't believe that makes them more successful neccessarily.