Why does almost all of the games have completely different plots and characters?

Because...the same characters and plots would get horribly stale? Besides, they all follow a basic plot; save the world. It just differs in saving the world how and why.

Except FF 12 wasn't about "saving the world".

Good for them.

Plus, X-2 was created by Square-Enix and not Squaresoft, it's just doesn't feel the same.

Basically each Final Fantasy is unique but by adding on the franchise name of 'Final Fantasy'... including a character named cid and some chocobo's and you have a game that will sell.

I'm suprised Kingdom Hearts wasn't labeled Final Fantasy!

When America bought most of squaresoft and changed to Square-Enix the Final Fantasy series totally had their traditions destroyed. The release of Final Fantasy X-2 ruined some, firstly no Final Fantasy has a particular sequel to one of the stories. Second, the battle system, they tried to make this into an action game but still keeping some of the more basic systems intact. The Final Fantasy battles traditionally are about tactics. If you go to youtube and watch a trailer of FF13 you will notice how it plays like advent children in some ways which wrecks the entire system. The ONLY thing they kept alive with the battle system is the fact the health is decided in numbers. I fear the day you will have "Bars". That'll probably happen to 14. As you can see I hate the recent changes in the game. Only ones who have played some of the more early games so far as 5 or 6 will be very unhappy with this whereas others who have no idea what has happened will think it's awesome. And more on the topic the storyline of 12 is terrible by what I've gathered. I hear it's basically a war between two cities and it doesn't even have a love story which is always the thing that is included in a Final Fantasy. They've kept it up for 10 games, but good things never last forever do they?