Baldur's Gate is my absolute favorite game... but quickly falling. I cannot beat this game! It is huge (five to six CDs, depending on whether you bot the expansion, which I did.) It sticks very close to Advanced Dungeons & Dragons 2nd Edition rules, though it does have adjustable difficulty. It is a great D&D experience, with such famous people in the Forgotten Realms as Elminster the Sage and Drizzt Do'Urden, who help you through your quest. Making a character is fun, though time consuming. Pathfinding sucks, as does the speed. The game is not fast paced (unless you get a pair of boots of speed and drunk on Oil of Speed), and the combat can become a tedious clickfest. It is very difficult. I reccommend it to those who love AD&D, Forgotten Realms, or REAL RPGs (as opposed to Nintendo and Sony powerplaying stuff).
