Here the big one will depend on your time and plans.
1) Trails of the sky remake - There's supposed to be a sequel, so it makes sense to play through it before it comes out. It's not very long, and depending on how much you enjoy doing side quests, the game can be completed in 40-50 hours.
2) Metaphor Refantazio - It's a good game, but you'll have to sweat for 70-80 hours to complete it.
3) DQIII - HD-2D remake - It's a very enjoyable game, relaxed, and even has difficulty settings. There are many improvements that make the game easier than the original, and it's not very long 30-40 hours.
4) Shin Megami Tensei V - There's not much point in playing the original anymore. If you can, pick up Shin Megami Tensei V: Vengeance. I'm a fan of that series, it's not particularly difficult (though some fights can be made significantly easier if you understand the bosses weaknesses and have experience with previous games). The average game length is 50-60 hours.
5) Ys X Proud Nordics - No matter how many times I tried to play this series, I always gave up, unfortunately, I don't like it. For me, the Trails of series is much better and more enjoyable than the Ys series.