FF7 could possibly never be topped. In my case, it would have to be a game that affected me on the level FF7 did, and it seriously affected my emotional side. To a level which just hearing some music from the game can make me cry godammit. The fact that FF7 was fantastic on so many levels (story/ characters/ music/ design/ graphics/ gameplay) makes it such a milestone. It's the computer game equivelant of Metallica's "Master of Puppets" (unless you're a Slayer fan...)
FF8 came closest. But after the disappointments that were FF9/10 (IMO) i don't think there's much going for FFXII, especially after Square-Enix totally sold out with FFX-2. *shudders* Paine was the only good thing going in that. It was less of a game, more of a masculinity remover.
I do hope some developer will make a game that beats FFVII. But in the present with more publishers only releasing games they know will make a profit (All hail EA) i expect just to see Half Life, Medal of Honour and Max Payne clones until I die.