Hmm..I have a long explanation here. I'll go in depth on every FF I've played.
FFI:
A decent game. It's simple, fun and easy to learn. The story is bland as well as the characters, but it has fun exploration and the battle system is actually quite fun. If you do decide to get this game, get the PS "Origins" version. They butchered FFI & 2: DoS by making it way too easy.
Different FF Games:
FF: Nes (Best One to buy)
FF Origins: PSX
FF 1 & 2: Dawn of Souls: GBA
FFIV:
Now this is an excellent game. The story is pretty nice, and the characters all have distinct personalities. What made me like this game is its difficulty. It is definitely up there with Tactics and FFV as hardest FF game. You can't just beat bosses by building up, you must use strategies and weaknesses to defeat them.
Different FFIV Games:
FFII: SNES
FF Chronicles: PSX
FFIV Advance: GBA
FFV:
This is an awesome game. The battle system is really fun, since you can change jobs whenever you want, which adds strategy to the game. The story is alright, but nothing special. The game is difficult, but fun to strategize what to do.
FFV Games:
FF Anthologies: PSX
FFV Advance: Yes to be released for the GBA
FFVI
I haven't played this game in a while. But it's pretty fun. It's the first FF game that actually has depth to it like the future ones do. The battle system is pretty much the same as FFIV, but a little bit easier. The characters are excellent, each all intriguing in their own way. I can't say much about this game, because I haven't beaten it..>.>
FFVI Games:
FFIII: SNES
FF Anthologies: PSX
FFVI Advance: Soon to be for the GBA
FFVII
Despite what others say, I do like this game. Even though the main character is a total annoyance, I found the materia system to be extremely addicting. The story is fairly deep, but not quite as good as the future FF games. The characters are a little..bland, with the exception of Aerith and Vincent. Still, if you can find this game, go ahead and play it. It's a good beginner's game.
FFVII Games:
FFVII: PSX
FFVIII:
I also can't say much about this game, either, since I have yet to beat it. Still, the battle system is either something you love or hate, which is a big factor on this game. The story, in my opinion, is a little crappy, but the battle system is fun, making it a fairly difficult game.
FFVIII Games:
FFVIII: PSX
FF Tactics:
In my opinion, the most addictive FF game out to date. But still, this game is only fun if you're pro-strategy games. The battle system is not like others, which is also another that you either love or hate. The story, however, is the second best FF story. It's filled with so much that you could spend hundreds of hours playing it.
FFT Games:
FFT: PSX
FFIX
This is another good game if you're a beginner. It's not very difficult, and has a battle system similar to IV's and VI's. The story is really good, but not quite the best. However, I give this game kudos to having the best characters in any game. They were so remarkable, which is one of the reasons why I loved this game.
FFIX Games:
FFIX: PSX
FFX
In my opinion, this and Tactics are tied for best FF game. This game's story is so great. It's so deep and amazing, and what makes it better than other deep stories is that it's not so complicated that you have to play through twice to understand. The characters is this game are good, but a few are just kind of boring. The battle system is pretty simple to learn and understand. It's a lot like FFI, because it's not active like most of the others I've played, but it has a few more tweaks to it.
FFX Games:
FFX: PS2
..I have played FFX-2, but am not going to put it up there cause it is not worth playing.
Now, out of all of those, since you're a beginner, I suggest starting with either FFX, FFIX, or FFVII. They are, in my opinion, the easiest of the FF games, and can get you started with the series. The choice is, however, all up to you.
