I liked Iris 1, though it did feel a bit dated. I really liked the humor in the game; the Engrish-speaking bear in the hidden village had me in tears from laughter. Some of the background animations were really endearing. I loved stopping in Veola's shop and watching her munch on food behind the counter. And the music! Man, what a fantastic soundtrack. One thing I really hated was that there's no way for any character but Klein to revive someone. If he died, you were screwed. The final boss fight was horse shit because it had an instant-kill attack; if it targeted Klein and you couldn't swap him out in time, may as well just reset.
Iris 2 was my favorite of that trilogy. It felt a lot closer to modern games in the series, and the battle system was so much fun trying to juggle enemies in the break zone to get high combo chains. The game wasn't that long, but the "twist" made it feel like you completed the game and are now going through the sequel. I liked that.
I'll be playing through both Mana Khemia games as soon as I'm finished with Tales of Zestiria. I still haven't played through the Arland games, either, but I picked up the Plus versions of all three when they were on sale and I'll get to them eventually. I did play the intro of Mana Khemia 2 just to try it out real quick, and I must say that I am not a fan of Laura Bailey's fake southern drawl. I hope it's not too grating throughout the game.