My favorite part of this game is building relationships with the non player characters that travel with you. Not to mention all the various side quests that are in the game. Each character class has different quests that are unique to each. For example the warrior has an opportunity to inherit a keep and protect it from bandits and the wizard can inherit a tower and train apprentice wizards in the magic arts and then have them create magic items for him. Because of these many sidequests this game has much replay value. And that's without the expansion pack. The throne of Bhaal adds another level to the gameplay. I must confess that I still haven't beaten the expansion pack but I have gotten far enough to know there are many plot twists. Another cool addition that wasn't in the first Baldur's gate is the ability for your character to fight with two weapons at the same time.
In conclusion, this game is probably the best thing you could buy if you like old school rpgs. However, be prepared to save often. Like the first Baldur's gate this game is incredibly hard but that makes it all the more satisfying when you finally beat it.
The Baldur's Gate series is one of the few games that has captured my attention to play the entire series all the way through numerous times, and at the end, still being disappointed that there isn't more. It is a shame that there will probably never be another game like this one. Neverwinter Nights doesn't even come close. I would HIGHLY recommend BG2:SoA and ToB. Go pick up the original BG as well, as it may help you to appreciate you character more being able to develop it from the beginning.
The depth of the story is perhaps its strongest feature. This is high fantasy at its finest. Continuing from BG I, the story follows the player as a Bhaalspawn, with great potential for good and evil. Players can choose which trach to take and which alignment they want to associate with. Want to be a Paladin paling around with a good cleric/wizard? Can do. What to be an evil theif with an evil mage companion? You can do that to.
The depth of the maps of the game are excellent, though in a few places you can get stuck because it is unclear what path is available. The game also includes several great improvements, like the character getting the chance to own a keep with its own special quests, based on which class you have.
The Throne of Bhaal addition brings the game to a great creshendow. I don't want to give up too much, but other planes and the possibility of godhood are in your future if you play through to the end.
The truth is, though I love the new games, I still go back every once in a while to play this one.