There are many things to consider here, but basically, yes, the CD album should be higher quality than the ADX rip from the game. This isn't always the case, but where it isn't the case is rare enough that it's not worth discussing. Mouser X over and out.
generally speaking streamed audio in games is lossy encoded these days. on the flipside though, sometimes soundtrack CDs are mastered weirdly/poorly and the music in-game sounds better (not too common though, and also can be subjective (loudness wars etc.))
myself, i tend to opt for a soundtrack CD before looking for a stream rip of a given soundtrack.
It's not all that super rare; modern games occasionally have PCM at CD rate (44.1khz) or higher (48khz). F-Zero GX, though, has 44.1khz ADX, which doesn't cover the full range of the 44.1khz PCM on the CD.