PMD1 music was good enough so that a few of its tracks got remade into the sequel as well (the Blizzard Island medley, both of the boss musics, and a few other things as well). EoS added yet more PMD1 remixes (I remember Buried Relic and Thunderwave Cave remixes are present in the Sky Peak areas, and Marowak Dojo got the Makuhita Dojo music). That isn't to say that PMD2 didn't have great tracks as well (Hidden Land, Craggy Coast, and Dusk Forest), but PMD1 was good enough that the stuff came back.