>>50409766I prefer Crystal mainly because of the way it looks and its 8-bit music. I'm just into it I guess.
HGSS are amazing and I love them, but one nitpick I have is that some buildings (such as the pokecenter and mart) strike as too modern and colorful compared to other more Japanese-looking elements of the towns.
Objectively, Crystal is not as complete as HGSS in terms of postgame repertoire, but it still has the Battle Tower, Stadium 2 compatibility and daily events, which is good enough for me. For how old the game is, it sure provides a content after you beat the league.