Well, there are a few...
First and foremost, Ys VI should be played (and if you have a PC, Ys-F is a must buy).
Secondly, I would actually say that Samurai Legend Musashi is worth playing. Perhaps this needs some explanation...
The combat system has received plenty of complaints, but with time, it can provide some serious fun. You basically come equipped with two weapons, the basic katana and one of several different swords that you earn throughout the game. When you lock onto an enemy, a guage fills up and the enemy will be highlighted. If a blue circle appears, you know that the enemy has a skill you can learn. When charged up, allow the enemy to attack while hitting the square button at just the right moment. You'll gain his new skill and can apply it to battle. You'll have large slash combos, spin slashes (spin the stick and attack), stabs (press towards enemy and attack), counters (charge up and attack right before they hit you), and tons of other attacks that use MP or SP (I think). Magic requires you to hold L2 while hitting triangle (normally, triangle attacks with your other sword). SP attacks simply require you to hit circle. X is then the jump button (and you'll be able to double jump soon enough).
The levels you move through are suprisingly interesting and fun. The lava area, for example, was loaded with tons of platforming, some simple environmental puzzles, and combat. It just fit together really well. All of the areas are interesting, though the second half of the "mining" area pretty much sucked (no platforming, VERY dark, and lots of tunnels). Most locations are fairly open, though.
The bosses are also quite excellent and actually pose a challenge. All of them are based on the whole "figure out the weakness" idea, but they are challenging enough that it keeps it very exciting.
The world is basically a collection of islands that you navigate via an overworld map. You travel on the back of a large flying creature which carries Antheum on its back (your home base). Antheum is basically a 3 floor circular area that you'll fill up with people as you rescue them in the field. Shops, training areas, story areas, etc. Not large, but not too small.
Now, one thing that really made the game more enjoyable to me was the soundtrack. Honestly, it was this very soundtrack that made me pick up the game in the first place. A combo effort of Masashi Hamauzu and Junya Nakano. What can I say? It's one of the best soundtracks to come out of Square in quite sometime. The Antheum itself, for example, isn't really anything special...but the music within is SO good, that I actually enjoy going there. Unfortunately, the voice acting is straight ass. Good lord, it could not possibly be worse. OK, to be fair, the main problem comes from Musashi...who was voiced by the same woman who handled Axl in the Megaman X7 US dub (which is one of the worst I've heard). Oh lord, it's just so bad.
The game lacks polish, though. The visuals are actually quite beautiful (seriously) and animate well, but the framerate is crap. Basically, they allow the game to run at 60 fps...but it can only hold that about 40% of the time. The rest is 30 fps (for the most part). Had they limited it to 30 fps, things would have been fine, but it jumps back and forth SO OFTEN that it really ends up looking awful.
I guess it's odd for me to give thoughts on this game, really, but Ys VI speaks for itself (and I've raved about it enough already).
Outside of those two...Dark Cloud 2 and Kings Field IV are solid. I especially dug KFIV. As it has been said, the game is VERY slow early on...but it really starts to grow on you. It also has the strangest framerate problems. It always runs at 60 fps, but your CHARACTER motion only seems to update at 30 fps. Kinda like the animation in Halo 1, where the PC version could run at 60 fps...but animation only updated at 30 fps. It just looks strange...