The Playstation line doesn't just have FF games. I myself have never owned or played a Final Fantasy game (except for Tactics, but that's a different type entirely), and I own the Playstation and PS2. I think the main reason that they have the graphics is to compete with the XBox 360, because that's what Macrohard is doing also (what has this come to?). Most games I've played so far for the Sony systems have had better gameplay than graphics, so I think that'll continue.
the PS3 seems to rely on its graphical capabilities (and FF fanboys) more than well-developed gameplay. Not to say that the PS3 doesn't have it's gems, it's just that it seems to be over-playing it's graphics as a crutch rather than a compliment to gameplay.
And anyone who buys a system just because they're obsessed with one not that great series needs a life.