Frank Kogan

Hm, pure K-pop-wise? I liked BoA, Wax, Uhm Jung-hwa, Lee Su-yeong and Park Jung-hyun (a.k.a. Lena Park) a lot. My friend went through a Kim Jong-kook phase a while back, so I have pretty much become a fan as well by sheer osmosis. (If you look up "사랑스러워" on Youtube, you'll see his major earworm hit.) Also liked Park Jung-ah and Lee Seung-gi, more recently (they're more pop/rock style).

Seo Taiji is really, really oldschool K-pop and he's been going in a completely different direction these days, but his later albums was what finally got me listening to K-pop after an adolescence of resisting it (I grew up in a Korean immigrant community, so I was surrounded by K-pop whether I liked it or not). Back then, what was popular was H.O.T., S.E.S., Brown Eyes, FinKL, and a little later, Bi and Fly to the Sky.

My latest favorite Korean groups are Apls (electronic group that can't make up its mind about what style it wants to be) and Bluedawn (which has already dissolved and become a new group)--I wouldn't call either of these K-pop though.

Oh and I just read the other referenced thread, and from my admittedly not-at-all representative experience, most of the differences in marketing the big SM groups is age. E.g. Super Junior is extremely popular among the elementary to middle school crowd, though obviously they have older fans too. I think SNSD also tends to be associated with younger female fans and Wonder Girls with older; not so sure if the age difference extends to male fans though. I would argue that the major class difference in listening preferences would be how much American/Western music you listen to, though sample size is too small to be positive on this.