I've played quite a bit of Tales games and I am very certain that Arise is the best game in the franchise so well deserved.
As for FFVIIR, I ended up enjoying that game more when I replayed hard mode and skipped its awful road sections and some cringe scenes.
If Arise is better, well, Arise does have more charm and is a complete story. But its not entirely fair, FFVII is obviously made on a far higher budget and part of an ongoing saga. I think both games have phenomenal battle systems though. Still, at gunpoint I would personally give the nod to Arise as its level design and gameplay is simply tighter. Tales of Arise is the best JRPG I have played in a very long time. Its better and more fun to play than DQ XI if you ask me.
As for why I think this is the franchise best, well I think it has the best story and least cringe. Its not an award winning story, but for this franchise its not bad. The combat, after a rocky start is up there with the very best. Each character plays very differently, and most of them are fun to play (Rinwell is one of the series best mages; she can steal and combine spells). MC can perfect evade and even gain overlimit mode from it, Kisara can perfect block. If you don't get hit using Law he builds up power, etc. Its all pretty cool.
The boost strikes never get old either, I love them. I think my faves are Kisara's. The one with shionnes bullets into her shield, or the ice shield with Do. Its great.