Only one! boom.

[Bolivar]

There's something we need to establish first:

What systems do you own and are willing to get a game on? Are you comfortable with emulation? What kind of display do you plan on using? Flat screen, old school round TV or computer monitor?

I agree with VeloZer0 about FFIX's combat. It would've been my first choice because it's the most FF-like FF and is arguably the best. It's the most well-rounded as none of its part suck at all but it doesn't reach some of the same heights other games do. And yes, the battles are painfully slow and the framerate is almost horrible.

FFVII has fast-paced battles because the camera's always hopping around everywhere highlighting choreographed battle animations. Everything is really responsive, you hit circle and Cloud's immediately halfway across the screen about to stab someone. In FFIX, you have to wait for your character to lift up his heavy sword, flip it around a bit, run across the screen, take a slash, and then turn around and come back. VII also has awesome pacing. TabbyTrap had a problem with FFXIII hardly being a game, and FFVII constantly bombards you with new and unique gameplay scenarios in the first five hours in the game. VII's also the best game in the series.

FFIV would be my next choice. It's FFIX-like but for an older generation and if graphics aren't a problem it's a good choice. It's also an awesome representative of what FF is and if you like 16-bit games (SNES, Genesis) you'll probably have a blast.

So without knowing what you have, my choices are
1) Final Fantasy VII
2) Final FAntasy IV