This thought just occurred to me when I was reading Mirage's reply over in Wonder Square..

Do you kinda mentally separate main series FF games from "side titles"/MMOs?

For example: I consider like I - X-2, XII, XIII, & XIII-2 to be main series titles while Dissidia, Tactics, and any spin-offs of VII to be just that- spin-offs. And of course I don't count XI & XIV as main series simply because they're MMOs, even though they're numbered like the rest of them.