I think this is the best soundtrack in the Pokemon series to date. The original soundtrack in GSC was the best and now this supercedes it with the great remixes and the original GB 8-bit tunes included to boot.
RSE and DPPt had a few great tunes (Slateport, Rustboro, Canalave, etc. comes to mind) but they were underwhelming as a soundtrack overall. IMO, GSC/HGSS has the best tunes, followed closely by RBY/FRLG, then RSE for a handful of truly great tunes, with DPPt coming in last with the least number of memorable tunes that sticks in your mind.