johto
This, as well as Kanto and Hoenn c: My sister still has FR/LG somewhere, I should dig it out and get used to the old Pokemon games again since Gold version's cartridge broke...
But I prefer the older games over the newer ones for some reason.
I also doubt they'll come out with Grey. If they do, it'll be that thing where they have the 2 games released at the same time (in this case, B/W), and then they add a 3rd with more features. i.e: Gold/Silver > Crystal, Diamond/Pearl > Platinum.