Its not the fact that the 3 lead characters are Girls which make it bad,what makes it bad is god awful characters them 3 are for instance,things they say :
Yuna: Oh, poopie!
Rikku: Yuna! Don't talk like that!
Yuna: I'm just copying you!
Horrible dialouge!,it completely destorys yunas character too,it makes her seem weak and dependant.ugh + people like that piss me off.
Things they do...i felt most of the game was a waste of time,the prpoer ending is the only thign worth while
as for the gameplay i hated the way you change clothes during battle it was just tedious + i rarely did it i kept Warrior on most the time and attacked.
The game doesnt last long sure you can do all them sidequests but to be honest i didnt really want to i didnt enjoy the game much at all.
As for the game Ruining the series.No, the other FF games are deffinatly still playable,even FFX but its deffinatly a downhill moment not that its risen FFXII was a struggle of dullness to play i liked the ending battles though it doesnt make up for 80 hours of a dull game.
I plan to get a DS now for FFIII and see how thats gone. (and becuase of the news theres going to be FFIV on there aswell)