Twenty years after its birth, Korean pop music has made its way from Seoul to Singapore to San Antonio to São Paulo and back again, "outbubbling" — as SPIN's Chuck Eddy phrased it last year — its Western counterpart by tweaking and perfecting the formula on which both have long been based. It's music that demands to be mainlined (hooks come sharper, choruses larger, visuals brighter), its gloss equaled only by the aggressiveness with which it's been delivered to the international marketplace in recent years. By now, K-pop's catalog of classics is deep enough to warrant a best-of list of its own, one we've assembled with our ears pointed to both past and present: The 21 Greatest K-Pop Songs of All Time, a singles wrecking crew whose final, odd-numbered tally is a loving tribute to one of the current moment's most beloved girl groups, 2NE1. DAVID BEVAN 21. SoolJ feat.