here are the archive.org links because the files are too large:
sonic 1: https://archive.org/details/SonictheHedgehogGEN
sonic CD: https://archive.org/details/soniccdcompleteoststream
sonic 2: https://archive.org/details/SonicTheHedgehog2
sonic 3&K: https://archive.org/details/sonic3_knuckles_ost