They're probably the closest you'll ever get to 'playing an anime', which comes with all the bad you can expect from that sort of thing -- usually very black and white morality, romances that they constantly shove in your face but do nothing with, characters generally defined by one big trait, generic stories, cookie-cutter fantasy settings, etc.
That said, I've mostly enjoyed the series. The combat is generally pretty funny, being based mostly around stringing together attacks, waiting for moments of opportunity, and dodging. One of the PS2 entries, Tales of Legendia, was actually developed by Namco's Soul Calibur team. They're also usually incredibly large games, offering up 40+ hours for the main storyline alone, and seem to be some of the last JRPGs to still offer up a ton of optional content.
Of the ones I've played:
Phantasia - A fairly light but fun game, though its gameplay is somewhat archaic now, having been the first entry into the series and all. It's seen a ridiculous amount of translations, both official and fan-made. The original SNES version still holds up pretty well today, then there's the PSX version which got two fan translations. Tales-Cless' translation of it is probably the most well polished of the two, having been in development for literally a decade, but Absolute Zero's probably has the better localization and is the one I prefer. The PSX version is a full-on remake, adding in new content and a new battle-system.
There's also a crappy GBA version and a recently released iOS one, both of which are in English and the only two officially translated. There's currently a fan translation in progress for the PSP version (Phantasia X), which is the newest and largest version of the game. Who knows when that'll be done, though.
Destiny - The second entry into the series (I think predating even the PSX Phantasia) and as such also pretty archaic and dated, with its biggest problem probably being the high random encounter rate. Probably one of my favourites, though. The story and cast is similarly light like Phantasia's, but it fleshes its characters out a lot more and they're not quite as generic, with Stahn probably being my favourite 'Tales of' lead. The game also has quite a bit of optional content, especially towards the end where you can pick up (I think) two of four optional characters.
The original PSX version is the only one currently translated and from what I remember, the localization was pretty decent (especially for the time). There's a full PS2 remake but it was never released in English, though there's currently a fan translation in the works but, again, who the fuck knows when that'll be done. This was also the first title to get a direct sequel but it never got an English release, but is currently getting a fan translation.
Eternia - This tends to be a lot of people's favourite entry in the series but I personally found it to be really bland. The battle-system gets a pretty large update here (it followed Destiny), making it more fluid and fun, but it's dragged down by its very bland cast and story. They tried to make it more somber but it just doesn't work, and your party is mostly made up of a bunch of boring characters.
Sympohnia - Probably thee fan-favourite of the series. It moves the series into full 3D, making its battles take place on a fully realized three dimensional field, allowing for greater mobility and a better range of tactics. It's a fairly meaty game, with it having taken me somewhere around 60 hours to complete my first time through, and I ended up missing a bunch of side content. It has an okay story for the series, generally managing to hit a balance between the lightness of Phantasia and the somewhat more somber tone of Eternia. Its cast is hit-and-miss, with Lloyd probably being one of my least favourite Tales protagonists but it has some good characters, like Kratos and Regal.
The GameCube version is the only one currently available in English. It got a PS2 port with added content but it never saw an English release. However, it is currently getting a HD PS3 release with the PS2 content plus some new stuff, bundled with its sequel, Dawn of the New World, though I never played that but it seems to be almost universally disliked.
Legendia - Made by Namco's Soul Calibur team, this one probably plays more like a fighting game than the others. One of the biggest changes is that it goes back to the more linear two-dimensional battle field, which is fairly limiting compared to Symphonia but I had fun with it. The story is fairly generic and not all that great but the cast is mostly good, with the game going for an almost comedic tone a lot of the time.
It was officially localized for the PS2 and they did a pretty good job with it. That said, there is one major fuck up. The game is split into two halves - the first being the main story and then the second being a series of smaller stories based on one particular party member. For some reason the localization team thought that second half was some sort of bonus content and thus didn't bother to record any voice acting for any of it, making the second half almost entirely silent.
Abyss - Going back to the three dimensional field of Symphonia, this one easily has one of the best battle-systems of the English released entries. They don't really change much compared to Symphonia but they do improve and fine-tune it, making it much more fluid and easy to use. The story is actually fairly decent this time around and even interesting at certain parts, complimented with a pretty good cast. There is one part near the middle that annoyed the shit outta me but it's fairly spoilerly.
It was released on the PS2 and later the 3DS, though I don't believe they added any content to it.
Graces - Whereas all the previous titles basically used MP for special attacks, this one uses more of a gauge that refills itself naturally throughout the battle, allowing you to use special attacks with much more frequency. The gauge refills depending on how well you fight, with doing stuff like dodging at the last moment and hitting a weakness refilling the gauge. The other big change is how the game utilizes 'titles'. Before in the series, a character would get a new title during a certain story event and it'd usually be mostly cosmetic, with no real effect on gameplay. This time, though, titles are the main way of unlocking attacks and add permanent bonuses to stats, as well as other passive bonuses. The titles then level-up as you fight, each having four passives to unlock.
The story is... okay, though it hits on the friendship theme way too hard and way too often. The cast ranges from bland to interesting, with my two favourites being Sophie and Pascal. They manage to flesh out the party fairly well, establishing a decent web of relationships between them, and all the characters get a decent amount of screen time throughout the entirety of the game.
The game was first released on the Wii but then re-released on the PS3 with more content, which is the version that got localized into English. The English voice cast is decent, though some of them take a while to get into character.
****
The others that have been released in English that I haven't played are:
Vesperia - This one seems to be universally loved. It originally came out on the 360, with that one being released into English, but then was re-released on the PS3 with bonus content. There were rumours going around of it getting an English release but it never did, though a fan-translation is in the works.
Innocence - Released on the DS, it was never officially localized but got a fan translation. I actually played this one for a bit but didn't get too far into it. It seemed decent enough, though instead of the usual party of four characters it got cut down to three, though beyond that it was fairly similar to Abyss.
Dawn of the New World - A direct sequel to Symphonia. It seems to have gotten mostly middling to negative reviews. There's apparently only two real party members, as one of the biggest changes is a sort of Pokemon-esque system where you can capture monsters and use them in battle.
Xillia - Reception for it seems mixed. As far as I know, it had a fairly short development cycle and it apparently shows, with a few reviews mentioning that its very linear. The game is kinda split into two as you get to choose which of the two main characters at the start is the lead, with some stuff playing out differently depending on who you choose. I've heard that not a whole lot changes between the two, with it mostly having been a cheap way of increasing the game's length.
Tempest - An entry into the series so shitty that Namco axed it from the main line up and now considers it to be some sort of odd spin-off. I really haven't heard anything good about it. It was translated as some sort of April Fool's joke, though how wasting two years translating a game you know to be shitty is supposed to be a prank is beyond me.
****
There's a couple of entries that haven't seen any sort of English release, those being: Destiny 2, Rebirth, and Hearts. Haven't really looked into any of them to comment but I do know each one of them currently has a fan translation in progress.
