Just finished Final Fantasy XV after getting it the Thursday before Christmas. Quickest I've ever run through one of these games (not talking just the FF series, either, RPGs in general). It's got a few gameplay problems, but overall, very good game.
Where would this rank in the FF series, kind of feel out with this series a while back. No excuse for FFXII!
Hrm. Mine might be the wrong opinion to seek then. I really enjoyed FFXII, though I wish the gambit system had been a little better developed.
As a game I'd place it somewhere in the mid-tier (around X or VIII). Story-wise it's pretty good for a FF, though the plot itself isn't one of the best (but are any of the FF plots, really?), the characters are some of the best the series has seen. It doesn't do much character development through exposition and generally eschews those dark shadowy pasts or traumas the series loves, but really makes you feel as if the main characters are some of your best friends you've been hanging out with forever. As far as villains go, well, I can't compare without spoilers, but suffice to say that there is only one other FF villain I really felt needed killin' as much as this one.