It's my favourite and generally seen as the best one. It's breakable as fuck though, but so are pretty much all FF games.
I have tried playing Final Fantasy 3/6 on a number of occasions. I have never been able to get that far in it (due to boredom/frustration), and to be honest I don't think it's (at least when played these days) a very good game.
My biggest issue by far - it's a directionless mess, with unclear objectives and many, many situations where the game is artificially extended by making you wander all the way across the world map to get to some location that may or may not advance the plot if you talk to a particular NPC at a particular time, but only after doing a side-quest for another NPC, etc. This happens even very early on, with characters telling you "go to this place" but not explaining, you know, where it actually is, and as I said, many things only trigger if you meet the requisite "wandered around aimlessly enough" quota, or have talked to every single character and then returned to a previous location with no prompting provided, etc.
A lot of the individual locations suck. Many of them are designed to be as pointlessly maze-like as possible... there's that one city where you have to climb those apartment buildings, for instance, which is pointlessly maze-like and has a lot of obscure crap that you won't figure out by basically mashing the A button on every single tile. I guess you'd call that "eleventh hour mechanics", i.e. stuff the designers decide to introduce at certain points of the game but not actually tell you about, making you rely on these obscure tricks to proceed even though you're never told what they are, how to use them, and you never see them in the game ever again.
The combat is extremely easy and requires very little strategy in party composition, item management, etc. Most of it can be finished by mashing the A button, even bosses. Good turn-based combat will make you think a lot about who's attacking and when... I never, ever had to think about this during the game. Even its puzzle bosses are pretty weak compared to later games like Chrono Trigger, which wasn't very hard either but at least made you figure out the right attack patterns and combos to win.
I guess maybe I have too high expectations, and you do have to give it some credit for being one of the first mainstream JRPGs that cemented so many of the genre's staples, but... that game just did nothing for me. As one of the JRPG genre's finest, apparently, I just do not understand the hype outside of nostalgia appeal.