It's pretty drastically overshadowed by the high quality of FFV and FFVI (though both of those games excel at seriously different things) - but I think it's a great leap forward in basic ambition for the series.
FFIV also has a very specific vision for its game design that is pretty heavily obscured in the Easytype version - it's probably the only heavily attrition-oriented game in the series until FF11/FF12/FF13.
What I mean is -- FF5 is all about having the correct party setup for the task at hand (and finding overpowered job/ability/equipment combinations), FF6/7/8 are all about everyone being able to pump out tons of damage, tank tons of damage, and heal a lot, so you pick your parties based on personality (until you get into the finer points of minmaxing/party optimization, but everyone is 'good enough' at everything), FF9/FFX are all about doing the most efficient action per-turn.
FF4, on the other hand, is 100% about finding the correct balance with every single party, in terms of your basic damage output/tanking/healing loop; the game *constantly* changes the makeup of your party on you (it's very intentional that nearly every time you lose a mage you gain a tank/fighter and vice versa) and every single time you've got to basically rediscover how much damage output you can do and how much damage you can take. This is what the game's row system is designed around; it's why Cecil is the most flexible character in the game -- capable of healing, tanking, covering weak party members, and tons of damage output, he's effectively the fulcrum of every party as it finds its balance -- and it's what makes the design of your final party especially interesting (Kain is already a character for whom you can make effective arguments for keeping him in the front OR the back row - Edge (with his extremely low defense) is much the same, forcing you to really figure out how you're going to configure your party in the endgame).
I think the story's pretty dull and the basic character growth system is too, but the constant readjustment of your battle-strategy loop to match your party and the challenges at hand scratched an itch that I didn't get again until Final Fantasy 12's boss battles. This stuff comes out the most in FFIV DS, but it's absolutely built into the foundation of the original game.