Well uhmm that's my first RPG game (back when we owned PS2). Till now, I still play that game!
Not trying to be a hater, XII certainly had a great battle system and fun missions, however, it had very lackluster characters and the story, to me, extremely shallow and boring. Perhaps the biggest flaw I saw in it was the two main characters, two of the weakest main characters in any of the Final Fantasy games I have played outside of the first one and X-2, which is saying something because I have played all of the number series games along with Tactics (the best Final Fantasy in my opinion if you count it).
If you haven't played any of the PS1 Final Fantasy games or the SNES Final Fantasy games, I'd say you would be doing yourself a favor if you give them a shot. I felt XII and XIII were lackluster, but I loved IV through X to death, and could only point out minor flaws in any of those games, all of them have worthwhile stories in my eyes and certainly have deeper, more appealing characters then XII or XIII. Tactics is also brilliant, one of my favorite games of all time in fact, however, be warned that it is a turn-based strategy game and for those new to those sorts of games, it can be a bit of a challenge.
Again, not bashing you, we all have our own tastes and opinions, just wanted to encourage you to give the older FF games a shot.
Of course it's a matter of opinion, but IV to X are indeed the best ones in the series.
Nostalgia makes games seem better, though.
I'd agree to a point. It applies to a couple of the Final Fantasies for sure, for example, IX. I loved the crap out of IX, couldn't get enough of it. I went back to it again and couldn't stop seeing flaws in regards to plot elements and certain characters. Necron was an awful choice for a Final Boss, Kuja was not that great of an antagonist either. Garland was a throwaway character, and on and on.
However, IV was just a brilliant RPG period and still fun as hell to play to this day. Outstanding characters all the way around, decent challenge so far as battles go, great villians, great writing, great everything really. You can say the same about VI, VII, and VIII as well, though I am biased towards VIII because it was my first.
Also Super Metroid, I defy any gamer reading this to go and play Super Metroid and not have a great time. Best game ever made if you ask me.