Well...

Old Gen:

FFI - Good.
FFII - Not as good.
FFIII - Never played T_T
FFIV - Very good <3
FFV - Meh, funny
FFVI - Masterpiece. <3

New Gen:

FFVII - Bad. Or very near that. And overrated.
FFVIII - Not as nearly as bad as VII, but still worse than most FFs. And it is overrated as well.
FFIX - Masterpiece. <3~
FFX - Okay, so this one isn't THAT bad, but Yuna... is just argh.
FFX-2 - FFX-2 does not exist. FFX-2 is an illusion of the great Hyne. Have a nice day.

So, yeah, Old Gen FTW