FFVII was my first and favorite game until I played FFIX. There was just something in that game that made me fall in love with it. The characters were lovable and even if a bit cliche, the fresh spin they put on their personalities made them completely unique and new.
I personally love settings in the middle ages, with castles, nature and babbling brooks, so it had a lot of appeal to me. Although FFVII was awesome, it was cold in a way where FFIX was warm and welcoming.
Also, for the first time in any video game, I thought the given couple was a great choice. Garnet was sweet, beautiful, smart and independent and fell in love with Zidane for all the right reasons. They got along in a manner that made you melt inside because it was just so damn sweet. I had no problems with her. She wasn't whiny or clingy like Aerith and Rinoa.
And Kuja will always be the greatest villain of all time in my eyes. The fact that his appearance was so outrageous drew my attention and then upon examining his character I realized how unique and realistic he really was. I liked how he wasn't fighting for power or wealth...he was simply doing those things to survive. He wanted to live. It's believable and made him human. Also, his dialogue expressed his theatricality very well, and I loved that about him too.
FFVII is still my second favorite, but FFIV is pretty close. I love games where you wander through glenns and valleys. Adventurer, knight or bard...doesn't matter to me. I love the midieval settings. FFIV has beautiful music as well, especially the world map theme, and the plot is addictive. It has a wonderfully ethereal feeling to it.
Well, that's basically it. I'll stop my ranting.