Played FF I, IV, V, VI, VII, VIII and IX before it (love most of them, my favorite is VI, not big into IX but still like it).
Played XIII on the X360. Found it beautiful to look at, the soundtrack was excellent, combat was very exciting. I think the plot is weak and I don't like the characters. That said, I really enjoyed the game, I think it's very good from a technical perspective. Very fun to play, I like the lightning-fast (pun intended) rhythm it has, meaning I like the linearity because the pacing was great. And yes, I'm a fan of exploration and open world/MMO-likes such as Xenoblade Chronicles X.
I played XIII-2 later. Beat it, didn't enjoy it as much. It was very confusing and making it more open ruined the pacing, in my opinion. I think the plot and characters are even worse in XIII-2. Still beat the game, still like it quite a bit.
Tried XIII-3 and quit after a few hours, too confusing for me (and the plot, dear God!). Might give it another go if it lands on Game Pass.
More info since I'm really talkative today ^_^ After playing XIII, I played X (really liked it) and XII (awesome game, even though I also didn't like the plot very much).