Yes, yes, game that saved Squaresoft, kicked off one of the most game successful franchises ever, blah, blah, blah. That doesn't mean it holds up today. Here's why.
The best thing I can say about this game is that it has really nice graphics for an NES era game. The character sprites are colourful and detailed, and all the weapon types and many spell types have their own individual animations, which I find impressive. The environments looks spectacular, though there's not much to see on the battle screen, sadly.
Gameplay does not fare so well. Though you are allowed a variety of classes (revolutionary as it may be), these classes are terribly unbalanced. The red mage, for example, expensive though he may be, renders black and white mages rather pointless, because red mages are not only much more durable and physically apt, but they can also cherry pick the best spells from both classes. Though there are certain spells he cannot learn, the ones he can are almost always the most useful. Thieves are basically underpowered Fighters, and, until undergoing class upgrade halfway through the game, worthless, unlike the fighter who is useful throughout. And Black Belts are perhaps the most broken of all, able to do massive damage without purchasing anything
except the occasional status buff. Other than the classes, there is the atrocious spell charge system, which guarantees you won't be using your precious magic on anything but bosses, and also the large number of obstuctive glitches in this game, even going so far as to have spells that do nothing. Which means that you've wasted your gold irrevocably.
The story is paper thin
, which is actually a huge problem. Considering the plot they were able to give Final Fantasy II (regardless of said game's quality), they could have done much more with this game. However, it feels unrewarding to sift through countless random battles for a few featureless player avatars. It doesn't work.
However, I will admit that the music sounds nice, at least. Overall, I couldn't finish the game, but thankfully, the Dawn of Souls remake makes it playable. It doesn't fix the balance issues (entirely) or the plot, but it replaces spell charges with conventional MP, fixes the glitches and as a whole, is presented much nicer as a modern day package. For me, it is the definitive version of FFI.