I've always been impartial to threads like these because I never know how to exactly state why FF8 is my favorite game, but after playing through it again recently, I think I have it figured out:

Despite the setting of the game, FF8 is the "most real" of the games in my opinion. The majority of the characters are well defined and understood. Each one has his or her own agenda which is sometimes sacrificed for the good of the group. As the game progresses, we begin to grow along with the cast and learn to expect what they'd say or how they'd react as if they were our friends or something along those lines.

Aside from all that, I find the music to be awe-inspiring, the story to be top-notch and a perfect pace for a love story, and the end of the game to be the most beautiful closing to any game I've ever played.

Not to take anything away from any of the other games, but for me, FF8 has that special place in my heart. Take care all.