I loved my Red and yellow versions when I was a kid, and then when Gold/Silver came out I loved them even more, especially with the ability to go back to the Kanto Region from the originals.
I never got any of the GBA versions, but I did get Diamond, and it was still as fun, there were some gameplay improvements like the flying and the underground(which might have been added in the GBA versions, don't know, don't care) but there was just too many to try try and catch and it didn't have as cool of an endgame as Gold/Silver/Crystal. Sure there was that island, but that's not really as cool or fun as 8 more gym battles in a familiar but oddly different location.
I'm sure Black/White will be more like Diamond, with even more monsters and even less of what made Gold/Silver so good.