Which Final Fantasy should I start with?

I'm relatively new to the Final Fantasy series (I briefly played IV on the DS a long time ago but stopped in the middle for some reason, although I did like the game) and I've been getting this urge to give the series another try. I've been thinking about getting FFXV since it's on sale at Gamestop currently but the FFXII remake was recently released and that also looks interesting. I've also seen lots of praise for the X/X-2 remasters.

I would prefer a game with fun side quests and a great story. I'm also looking for deep character progression and combat.