If I'm honest I never actually liked GSC...if I ever felt the need to play an older game around the time of RSE I just went with Red usually. I did play GSC all the way through when I got them, and I did get all 3, but it was only later I sort of looked at them and something about them really didn't appeal to me - it didn't seem like a Pokemon game, I dunno...but HGSS were amazing! I think my favourite part was the Pokemon following you around, I wish they wouldn't remove that haha.
I also loved the new sprites - one that always stands out is Mew, I loved its Gen III sprite but hated its DPPt one. They made a nice one in HGSS and went backwards in Black. :(