My list goes like that:
1. FF VI
2. FF V
3. FF IV
4. FF I
5. FF II
These are all I played. I remember reading a review about FF X when it was new, and I was quite jealous that I couldn't play it, so I guess I would have liked it. And yes, I prefer V over IV (I seem to be the only one) because I think it is just much better gameplay-wise.