Well, here are the imrovements to FF1 since the NES version. Never played the PSX remake or the WSC version.
--- Obviously better visuals. Everything still looks the same, but much better. If you know the NES version inside and out, you'll notice all the enemies are in the same poses, just illustrated better. For instance, the trolls still look like they have migraines. Spell effects are easily of FF4 quality. Attacks are longer than two frames. There are even a few cinematics, like when you get the bridge built or raise the airship.
--- The text makes more sense, as do the enemies' names. Some of the dialogue has been lengthened or otherwise made better. WARMECH is called DEATH MACHINE once again. All the Nintendo censorship of old is toast.
Dead horse is gone. Party members automatically target a random enemy if their original target is killed before their turn. That was easily the most annoying part of the original version.
--- There were a few odd changes... Like no silver equipment in the elf town, and Matoya's got some sass. The dwarves are all scottish now, but one of them greets you in the FF dwarven way, Lali Ho! Cool.
--- They also added bonus dungeons with cool rewards for beating the new bosses... But JESUS! The Soul of Air dungeon is like 40 FLOORS DEEP! With multiple bosses at the bottom of each dungeon, you have to make four runs through the whole thing to get all the bonus items.
--- Hey hey, everyone's favorite octopus shows up as a bonus boss, and he's all set to jam up the opera, kekeke.... That's right, Ultros is ready to kick some light warrior ass.
--- From what little I've played of FF2 for Famicom, I can tell the current remake is far better.
If I weren't eating ramen for dinner, I'd buy it. It does no disservice to the originals. Easily one of the top five GBA games available, definitely THE purchase if you have any love for RPGs. Metal Slug takes the Contra crown. Minish Cap would kick major ass, but it's kinda short... and that kinstone shit is royally tedious.