I love FF 1-9, after that, I'm not a fan.
FF7 is the best in the series, followed by FF9 and FF6. FF8, although good, is the worst out of 1-9.
FF10, 11(MMO), 12, 13, 14(MMO) were all not that good in my opinion.
If you are playing FF7, then be prepared for one of the, if not the greatest JRPG of all time. The story/characters/weapons/leveling system don't fully open up until about 10 hours into the game, that's when you realize how amazing the game is, and it never stops from there.