i dont platinum a game unless i really like the gameplay and im two trophies away now
i platinumed ff13-2 as well
but i'm not going to platinum ff13. :s
they are all very different games so it's hard to compare. in terms of battle system, this one is the hardest to learn for me. too much happening at once, and i couldnt keep up; i was used to a more spread out paradigm system in the other games, and here i was out of my element. the stagger gauge being a whiny sin function didn't help matters, it seemed arbitrary at first. i didn't like having a team, but it added to the solitude uberlightning was supposed to be feeling i think. the party additions in 13-3 don't really count. they're extra spells but you can't modify them in any way.
story? it's the same story that just continues. they wrap everything up nicely, but a lot of it you have to assume things were clear for previously, which i never felt like they were, but that wasn't an to me issue after the second game. ff13 took itself too seriously, with all its holes, to be taken seriously by gamers i think. ff13-2 didn't care as much and took a more lenient route towards story and continuity, and it knew it too (one of the reasons i enjoyed it actually). ff13-3 was much more balanced here, and i liked that about it as well (moogle throwing and theological questions all at the same time)
world/atmosphere, i felt like LR had the best one. it was most coherent, in a way. ff13-2 was a jumbled thing because of the span of time it took to explore the world, and the world developed without your involvement for many many years. no such missingness in LR, where you see how immortality has affected a people, and you mingle with a society that has been hurt tremendously by being given eternal life, in a way. most people in LR are either in disbelief the end is near, or are looking forward to it, it seems like. this is a crazy thing to feel in a video game. LR is still plauged with the weird exposition/monologue story pieces that the previous games had, but the writing's better and tighter this time around. lumina rocks the show and certainly adds to the atmosphere.
the concept is much better than ff13, where you're fighting a big bad sole entity who dragged you into this/big bad govt, and ff13-2 where you fight _the passage of time_. in ff13-3 you are fighting both the actual LOSS of the passage of time, as well as the impending equivalent of heat death in the end. bhunivelze is a nice personification of it, but there's deeper themes here, like perserverence in the face of complacency.
the world design itself is difficult to gauge. i think ff13-2 was prettier, but ff13-3 was more thought out (and even there it still could've used polishing). was happy to see less corridors this time around. even ff13-2 was very corridor happy. ff13 isnt even in the running compared to its children. it was boorish and pragmatic and it makes sense storywise, but its not a fun place to be and experience in a video game. in ff13-3 however, i enjoyed my time. same with 13-2, but in ff13-3 you have time to develop a connection to a place, and in 13-2 your connection never lasts.
i also like that you don't gain exp from fighting. i also had beggars beads on the whole game so i didnt get gil either. it makes more sense this way.