As stated, most Mothership Tales games are worth investing into. However, I started to play the Tales JRPGs more or else for the gameplay and a little less on the story.
As a fan of JRPGs, emotional attachment plays big on the preference. So I'm going to rate overall based on what I have played:
Symphonia: Someone stated that conceptually, Symphonia is a thought-out and sound story, but should have been a shorter game. I agree with this somewhat. The game thrives on pointless cannon fodder to exist within the main plot. It plays very heavily on the theme of devastation (despite the point being regeneration or reform). If you play this game, expect tragedies of all types to occur. The game is pretty simple and emulates the overall tales experience efficiently and effectively. Combat perks can lure action RPG specialists and fighting game players alike. For what it was in its time, it's very well worth the investment for a couple of runs.
Dawn of The New World: If any story had a weak followup, this would be it. Characters early game can be generally unlikable (unless relatable although subjective). Combat doesn't feel fluid in comparison to Symphonia or Abyss. There are axis problems when characters combo on the human cast. It is drastically different from one another and it may implicate that there was no intention on fighting human enemies in the first place. The game has some neat perks but those are mostly subjective. Play it for what it's worth. But at the end of the day, it's pretty obvious that it was Bamco trying to do the bare minimum to fix their debt.
Graces F: The characters. If there's anything Graces is really remembered for, it's the characters. The combat is a nice spin on the CC system, being in 3D. The plot is really predictable (given it's about friendship) and I don't really recommend it if you're not into that sort of plot archetype. The way it handles titles is very foreign from previous tales games and feels extremely overwhelming. The game is really about type resistance and type advantage so if that's your type of game, go for it. It is more emphasized in this game than other games I have played. Overall, if you somehow find out you like the game, then it's worth your money. I paid $30 for it and I'm honestly glad it wasn't the full $60.
Xillia: Game has some interesting concepts and doesn't utilize them very effectively. It gives the option to select a male or female protagonist, both of which are in the story as their own character and are influenced based on perspective. Budget is notably lower because the models in game are actually worse than Vesperia on the 360. The game reuses a lot of assets (but then again, what tales game doesn't). Combat is fairly average but doesn't convey as much depth as older titles. The up side is that the game can be easily beaten in 20 hours, but warranted at release for $60 dollars was not an investment I was going to make. Waiting for the price drop seemed to be the better choice (though I got a digital copy for free from a friend).
Xillia 2: The Debt System. This is arguably the most disliked feature I have ever experienced in a tales game by far. The scope is too realistic (and annoying) and doesn't really contribute to many perks at all (though you CAN get some neat stuff for paying on time). The main character is a silent protagonist and the concept with this would have worked smoother if all the other characters didn't talk. Unfortunately, they all do and it makes it come off as extremely awkward. It doesn't make much landscape improvement from the first game (given, it is a sequel, so changing too much would hurt the nostalgia of the players of the first Xillia). The combat does make subtle improvements but the AI wasn't one of them. Watch any tales solo and you will see that the game is essentially a combo-fest. Story had some holes in its original plot (though both games had holes) and they attempted to make the cast more lively by having them come and leave when needed. This is vaguely similar to Symphonia 2's situation with the original cast, and replicating it wasn't a smart idea on Bamco's behalf.
I have played more titles but I wanted to highlight those 5 because I've either beaten them or have spent at least 10+ hours in them already. To be blunt, you can play any game in the series and get the same old experience. The difference being the setting, the battle system, the writing and all that other junk. It all comes down to preference. I can see why people like the games they do and it's really up to you man.
But to really be honest, I think Vesperia and backwards is my preference. Though be warned, there is a HUGE gap where Tales isn't localized during that period. If you know some Japanese or have gotten used to the menus, it's worth checking out. Otherwise, play what has been localized already.