Final Fantasy VI SNES and PSX - Very good, though old and 2D, it is still a classic and is very well put together
Final Fantasy VII PSX and PC - Was a very good game in my opinion, certainly recommend it, labelled as the best.
Final Fantasy VIII PSX and PC - This was very good as well, but not as good as some.
Final Fantasy XII - Is very good, though I think it's a bit stretched, I mean there are too many periods when I need to battle and level up, which is a down point to the game, I mean I'm 40 hours in the game and the plot is picking up. I completed FFVI, VII, VIII and IX in less than 40 hours...even with side quests. (Though IX was pushing the 40 hour mark with the chocograph side quest)
Final Fantasy X - Was quite good, in terms of plot it doesn't have the same greatness, but you've got some newer game play in there and different features.
Final Fantasy X-2 - Keep away, trust me, don't even think about playing it...it is a terrible sequel to FFX, if waza online was still up with my reviews, I'd direct you straight to my FFX2 one. Gameplay wise, it's good, it's just everything else stinks, especially as the main characters are now tarts.
If you want to get started, you're probably going to find yourself going into Final Fantasy VII quite easily IMO. It was the first one I played and probably the first Playstation game I played and fell in love very quickly.
Hakuna Matata