If it were not for Kanto, G/S/C would have been boring games. The Johto region does not offer enough to warrant it a standalone. The Rocket subplot was not fleshed out enough (not even in HGSS). Obviously RBY are the worst games on this list, but nostalgia will prevent a lot of votes.
I voted for DPP, because I did not like their changes to Hoenn's contest formula. :P That, and even six years later Sinnoh still feels like a labyrinth. But I do very much miss the Pokétch.
... Black 2/ White 2 does a whole lot better imo ... not sure why.
Still i liked HG/SS the most ... really i spend hundreds of hours on that game ... why wont they let us walk our pokemon again, i want them to follow me around like in HG/SS ... that was awesome :-D --- Hey i'm not camping ... i'm "tactically waiting" :-D