I don't really have a favourite OST. My favourite songs from FFIV To FFVII (For Now) include, extra comments included in some:
FFIV:
Boss Battle Theme (Popular Enough To Appear In Super Mario RPG)
The Final Battle
Moon Cavern
Red Wings
Another Moon
Illusionary World
FFV:
The Battle (Probably my favourite random encounter theme in Final Fantasy)
Cursed Earth's
Walking The Snow Mountains
The Fire Powered Ship
The Day Will Come (Depressing)
Battle On The Big Bridge (The Original One And By Far The Best)
Beyond The Deep Blue Sea (Just Awesome And Relaxing)
The Prelude Of Empty Skies (Final Dungeon Theme With Cool Build Up And Eery Beat. This Is How You Build Suspense)
The Decisive Battle (Exdeath/Exodus Battle Theme)
A New Origin (Badass Ending Them With Crazy Mode7 Graphics. Also The First FF Ending I Ever Experienced)
FFVI:
Edgar And Mash (Very Regal Sounding)
The Serpent Trench (I Swear Every Uematsu Underwater Theme Has The Same Atmosphere, But Damn If It Doesn't Work)
Terra's Theme (Also The World Of Balance Theme. So Dramatic.... And Set's A "Got To Do What Need's To Be Done Tone")
Spinach Rag (RAGTIME HO DOWN!)
Aria De Mezzo Carattere (The Opera Song That I Swear Sound's Like Aerith's Theme From FF7. Actually No It IS Aerith's Theme For The First 15 Notes, Compare The Two)
The Wedding Waltz (Classy)
Grand Finale (Almost All The Opera Sequence Had Classic Music)
Setzer (Flight, Like The Man Himself)
BlackJack (Airship Theme, They're Always Good. I Feel Uematsu's Invoking A Feeling Of Rising Above Your Trouble's With This One And It's Fitting And Works)
Relm (Relaxing)
Dancing Mad (Freaking Long And Epic. The Best Part Comes When You Face Kefka And The Church Organ Comes In. Also The Way It Segues Into Each Portion As You Fell An Enemy, Yet Always Manages To Sound Natural Is Just Cool)
FFVII:
Cloud Strifes Theme (Great Map Music As Well That Get's Replaced By A Crappy Noise That Sounds Like A Prolonged Fart Later In The Game)
Bombing Mission (Intense)
Mako Reactor (Creepy)
Hurry (And It Makes You Feel It)
Honeybee Manor (Just Bizarre)
Flowers Blooming In Church
The Shinra Corporation (It Sounds Like A Wrestling Intro To Be Honest, But It's Ominous And Unsettling, Like The Company)
Crazy Motorcyle Chase (It's Actually Called That)
Fortress Of The Condor (Military March)
Rufus Welcoming Ceremony (Again)
J-E-H-O-V-A
The Gold Saucer (Circus Music)
Valley Of The Fallen Star (Pow Wow Music)
The Great Warrior (Dramatic)
Those Chosen By The Planet (Sephiroth's Theme. Really Creepy)
Cid's Theme (Uber Dramatic Parachuting Getter Done Music)
You Can Hear The Cry Of The Planet (And It Sound's Like A Moog)
Aerith's Theme (BWAAAAAAAAAAAAAAAH! Just Kidding)
Buried In The Snow (This Is Like The Underwater Theme Only Under Snow)
A Secret Sleeping In The Deep Sea (Just Kidding This Is The Real One)
Judgement Day (It's Called Judgement Day And It's Ridiculously Dramatic.....YEAH!
)
Birth Of A God (Rock On)
One Winged Angel (Touched Off A Slew Of Gregorian Chant Style Copycat Themes In Later Games)
I'll Pick This Up Later....