Yeah, I like G/S/C. I like the radio tower and how you got to to Johto and Kanto. The game had alot of cool features like the night and day thing. But I like R/S/E because Team Magma/Aqua and the Secret Bases.
Emerald, without question. Better graphics, more Pokémon, better gameplay, better music, Battle Frontier, 2 vs 2 battles, more strategy, contests....I could go on...It was R/S/E that made me love pokémon as much as I do.
Definately Emerald above all. I could go on and on about the BF. It has had me entertained for nearly 6 months now. Not to mention secret bases, cool plotline, just loads of extra stuff to do was great.
XD is my second favourite, the attack animations are so cool.