What is your "favorite" Final Fantasy game? Why?
Very hard question. It's a solid four way tie. [AM I disqualified? O.o]
Final Fantasy I was the first game in the series I played. My cousin introduced me to Final Fantasy by showing me the game back in 1993/1994. Shortly there after I began playing on my own--he left me his NES and the maps and manual (somehow got lost in my parents second move). For nostalgic reasons, this game is no. 1 It introduced the hyperbolic irony that was to be "Final" Fantasy as it's creators honestly thought it would be their last game before the company folded. The music from I, II and V are still my favorites.
Final Fantasy IV was the first game in the series I played on my own (along with Final Fantasy VI). They were part of my first foray into gaming--I rented Final Fantasy II (US), Final Fantasy III (US) and Secret of Mana (US)--each for SNES. It was by this point I had fully comprehended the vast importance of these games and became obsessed with all things Final Fantasy.
Then came Final Fantasy VII. I won't say that VII beats the storyline for VI, because that would be mere hyperbole. No one can say definitively, which is better. VI had the villain who you could not understand--who just felt evil--and who you just wanted to kill--it was the Opus Epic for the Final Fantasy Series. It even had an Opera specifically made for the game--a very good Opera! (as Operas go)--and has left many fans claiming for it to be awarded the prized claim "best in series". But, Final Fantasy VII did accomplish one thing no Final Fantasy game has before or since accomplish--made the series known. It was the only reason I got a PSX. When I saw that TV ad for Final Fantasy VII, I had to have it, NOW! The game had depth and great character development (just as VI had), but the characters were unique--they broke with the series's predecessors. Up until Final Fantasy VII all the games were either pure fantasy or fantasy/steampunk. Final Fantasy VII brought the Cyberpunk modern era into the fold and created a real modern era science fiction love story epic. Gasp! Long! It even mixed in tragedy in a way, previous games have not!
Final Fantasy VI on the other hand took an evil Empire vs. an evil Corporation. Final Fantasy VI was a story about how revolutionaries can save the world from and evil Roman Empire plus magic and crazy ass techno-steam punk powers! Final Fantasy VII landed far closer to home--corporatocracy: When civilization and society sell out to Corporate Japan, and the world is left in their hands, to do so as they please. Governments fall, and Shinra Electrical Power Company steps in to "save" humanity from itself--or so they claim.
Sorry for my length, but I really could not choose any one game to be my favorite. I didn't even mention another personal favorite Final Fantasy V. Choosing is just so damn HARD!