Off the top of my head:
>Shiny Pokemon Egg from Daycare (Which, in turn, was actually a modified event from the Japanese version which required the GB Phone adapter).
>Suicune event at Tin Tower moved to Cerulean Cape and different.
>Celebi Event changed to stupid fucking worthless Pichu event.
>Animated Sprites
>Your room customization (Which was also in GS)
>Certain Pokemon locations, some stayed while others used their GSC location.
>Kris
>Rooftop of Goldenrod Department Store
>Mystery Gift like it was in the originals
>Mt. Mortar changes.
>Couple of NPC trainers teams were modified for Crystal and had GS teams instead. Pretty minor
>The Ruins of Alph extra stuff that was added in Crystal as well as the Unown Dex and being able to print out stuff.
>All of the Pokemon GB Phone Adapter stuff in the Japanese version.
>Goldenrod Move Tutor, but it was redundant since all the moves were pretty much TMs at that point.
Honestly, Outside the Suicune stuff and a few minor things, Crystal really did not have too many differences from GS. Pretty much all the major stuff made it into HGSS outside Kris.
