I decided not to listen to the critics and picked this one up as there weren't a lot of good "classical" DS rpg's since Dragon Quest V and found that I wasn't disappointed. Despite it not following actual greek mythology, I found this game to have a fairly enjoyable story with some pretty good DS graphics, and a pretty interesting twist on the battle system. And it's a good thing that the battle system was fairly engaging, as you will be in a LOT of battles (random or otherwise). I actually enjoyed the little mini-games that you could play when you chose a certain magic spell or skill to use to help increase the damage/effect it produces in battle. Of course, you could just "auto" your way through everything, but it makes it far less fun. There was also a fair bit of strategy to how you set up your party (formation, equipment, etc.) that made the battles a bit more interesting.
As for the story you play as a group of immortals who have lost their memory (Lost Odyssey?), and want to trek to Mt. Olympus to find out their destiny and who they are. You are supposedly Heracles, and along the way in trying to find yourself, you meet about half a dozen other so-called "Heracles". The humor is cheesy, but I thought the writing was sound enough (minus a few bits) and even laughed out loud at a few gems. It's a story that will keep you engaged throughout the 40 or so hours you play this game. Yes, it's about 40 hours long (about 20 is battles), so if you don't have the patience for that in a DS game, don't pick it up.
A few gripes: the camera was odd. Even when I changed the angle, it would just reset itself for no reason. There are also quite a few moments where you just CAN NOT SAVE. I would be sitting through about 15 minutes of dialogue waiting for a point so I could save to rest my eyes. I also had trouble activating certain on-screen items like chests and such. Otherwise, this is a gem of a game with amusing characters and a fairly engaging storyline.