I admit I had reservations about this game after the excellent Suikoden II, but it was all for naught.
After the grand epic storyline that was Suikoden II, Suikoden III is a much smaller and intimate game than its two predecessors. The focus here is on the characters, as opposed to the greater conflict.
The big change in this game is the addition of the Trinity Site System, that allows the player to play through the story from the point of view of each of the three main characters, Chris Lightfellow, Hugo, and Geddoe. This shortens the story length considerably, but gives you a better understanding of it. There are also improvements to the fighting and battle systems, that give you more control over the fighting and less of a random feel. The duels remain unchanged.
The other big change is the switch from 2D to 3D, but other than a slight change in the clothes (ex. no more big goofy hats) the characters are transitioned well to the world of 3D. Lucia & Sasarai look much better than they did in Suikoden II.
Where this game disappoints is in the music, which aside from the opening theme doesn't seem as inspired as it did for the first two in the series.
Overall, Suikoden III gives a different feel from the first two games in terms of story, and is easily the best looking and playing game in the series. It rivals Xenosaga for the best PS2 RPG. 9/10