Dungeon Siege 2 is solid and fun game that has a lush world and some major improvements over its prequel.
The major differences between DS1 and DS2 are the AI, addition of skill trees, sub quests, and explorable areas. The world is lush and densely populate both with treasures and monsters. As you wind your way through the main storyline there are many extra quests you can do that will provide you with cool and rare items to help make your party more powerful. There are also many extra areas which contain hidden treasure or minibosses that have better than average loot. These places are mostly obvious to find if you aren't lazy and are using your map.
The AI in DS2 is both an improvement and a hindrance at the same time. For those people who enjoyed the original fast paced game style of DS1you will see a significant change in regards to this. The AI is much harder even on normal. The AI is smart will flank you, pop up from the ground, run away when hurt, attack a healer (which is very helpful to have in your party), and even attack a person for drinking a potion. This new improved AI greatly slows down the overall pace of the game. It is very difficult if not impossible to make one "super character" and rush through the game solo. This is all fine and dandy but, the part I did not like was you are required to wait until you beat the game the first time on normal and start a game on veteran to get your fifth party member. The same thing applies to the sixth party member, you must beat the game on veteran difficulty before gathering you're the next addition to the party. Your party size is also reduced by two meaning the maximum party size is now six and not eight, and considering the difficulty with the improved AI having 8 members would be helpful. On the plus side the other party members now have their own personalities and interact with each other based on who your party is made up of.
The level has also been modified but this is one of my favorite new features. On reaching a new level you now get skill points to spend. And you can put these into a talent tree that enhances that characters abilities for many skills. As an example if you put points into one ability it might reduce the mana cost of casting nature magic spells. As you fill out these talent tree unique and powerful special powers are unlocked that are great for some of the tough or heavily populated areas. Some of these powers range from single super strikes to invincibility (time limited). All of your special abilities are capable of being raised to rank three by adding skill points to the corresponding skills.
With all this Dungeon Siege II can easily provide 20-30 hours of entertainment. I feel it lacks much replayibility and the multiplayer seems weak for the most part. If you can pick this game up for a decent price it is worth playing through the single player even if it is just once. The world is lush and fun to explore, the AI is smart and provides a decent challenge. You can expect your party to find much cool loot, die, and become "heroes" through all of this you should have a fun time playing this game.