The last months I've been playing all the YS games.
I have played (in THAT particular order) (all steam editions)
Ys I & II Chronicles+
Ys 3 Oath in Felgana
Ys 4 Memories of Celceta
Ys 6 Ark of Napistim (I had played the PS2 edition many years ago when it was still new)
Ys Origins (played Tovac and Fact, and got to burned out to play Claw. I might go back for him after Seven)
Ys Seven (currently playing...)
Ys 8 Lacrimosa of Dana (next in line)
They are fantastic games, but also weird how Oath and Memories are so clearly better than Ark and Seven (since they got made later) despite being supposedly later installments. It's also annoying how there is no remake of Ys 5 yet.
My current worst is one that others consider best, origins. It could have been a very good game on it's own, but playing the same stages, bosses and main story 3 times is to much, even if the characters are different.
Despite the nit-picks, I'm an YS fan now!
I've also been playing Tales of Vesperia PS4. But it's to long and I took a break to play Spiderman which is much smaller and definitely more addicting and worthy of marathoning.
Vesperia's main problem is it's age. Graces had much better gameplay and mocaped cutscenes, despite the shitty graphics and story. While the graphics should have been mindblowing back in the day, they are just plain good now, so they can't keep me hyped to overlook the other flaws.
Next in Line is Yakuza Kiwami 2 that I've just ported from the US, since I wasn't able to find a standard edition here.