I agree, Gold/Silver was probably best of the series to date.
1: Excellent Music for it's time.
2: The Pokegear was full of useful utilities.
3: The week cycle and changes from day to night.
4: The story. It felt like it actually occurred in the same universe as it's predecessor, and literally picks up 3 years from where the last game left off.
5: There were entirely too many things to do. There really isn't much of a post-game in most of them, but your first showdown vs Champion Lance is probably the half way point in the game.
I enjoy the music of the newer games, and I enjoyed the nostalgia factor of the re-makes (that, and finding the G/S pokemon was bloody difficult after the move to the GBA). Black has a surprisingly deep plot, though.