there're things I liked about XIII-2, but if you hated the battle system for XIII, you're not going to be majorly impressed by the changes in XIII-2, though they are different.  I've never played Rogue Galaxy, but I've always wanted to.  I've heard it's got a good sense of humor, and even though it's old, cel-shaded graphics tend to age better than normal PS2 graphics.  For instance, DQVIII still looks marvelous to this day.  

Having not played any of those games, including FF XIII, I would probably pick up Rogue Galaxy.

I still own Rogue Galaxy for PS2 and it is fantastic, one of my favorite games actually. If you haven't played it, give it a try. As for 13-2, I enjoyed it a lot too. I should warn you though, if you want to get through 13-2 to get to Lightning Returns, LR is nothing like the previous games at all. Actually it is quite stand alone even if it does tie up the loose ends for 13 saga. 

In all honesty, I just want to get the XIII series done and over with.  Besides XI and XIV I have beaten every Final Fantasy game, it's just so sad that the franchise has taken a turn for the worst.  Even the demo for XV I found to be very boring.  I wish Final Fantasy would do what Dragon Quest has done, and kept the same tried and true formula with very minor tweaks for each new game.  All in all, I miss my favorite game franchise.

As someone who takes the Final Fantasy series very seriously, I'd say you'd be fine not playing the "sequel sequels" if you don't want to. That said, I loved FF X-2 and really enjoyed XIII-2, but I found Lightning Returns to be a god awful mess that I couldn't be bothered to finish. So I'd go with Rogue Galaxy. I didn't get a chance to play it at the time, but it was when Level 5 was really coming into its own as a developer.

You should try Bravely Default or Legend of Legacy then, if you own a 3DS. They are basically retro games with new skins. Also, mobile is getting a retro style FF game called Brave Exvius. Oh and Record Keeper on mobile is also very good--and free!

Is that right?

I played a few hours of Rogue Galaxy and liked it. I bought it but then didn't get to it. It's high on my list of backlog games to play. I love everything by Level-5. 

I agree, they haven't made one game that I have disliked.  Even Jeanne D'Arc for the PSP was great, despite not really like tactical RPG.  

I played a few hours of that and liked it. Want to play more. 

I am going with Rogue Galaxy for 2 reasons.

1.  I want to play that more

2.  I have to do laundry, and my PS4 is down stairs next to the washer and the PS3 is away from it.  I need to be able to hear to hit a switch, so that played apart in the pick as well.

I scanned this Rogue Galaxy advert from an old comic a while back.