First some disclaimers, I have not played Final Fantasy XV and my opinions are influenced by third-party information. My opinion may change once it comes out on PC. Now for my credentials, I have been a long time fan of the series. I have played all of the Final Fantasy games in one form or another (excluding Final fantasy XV).
I first started playing the series when I got Final Fantasy VII (Yay! Remake FTW!) back on the PlayStation, I remember the awe I felt at the scale of the story. I remember enjoying the puzzles and the various secrets that you could discover and have other fond memories of the whole game. Dressing poor Cloud up in a dress, or owning the various Jenova bosses and unravelling the mystery of Cloud