To begin, Baldur's Gate is a great game. It's incredibly deep, the characters are interesting, and the world is massive. However, the combat is clunky and requires pausing every 0.5 seconds or so. Also, the randomness of combat is such that saving before each one is pretty much a requirement since if your main character dies you need to load a game. Finally, the difficulty overall is very high, and it's easy to stumble into a random encounter in a low-level wilderness half way through the game and still get owned. But if you'll put up with the frustrating elements, it can be a wonderful experience.
If you like having many ways to solve a problem, this one's for you. If you like exploring strange and twisted worlds filled with strange and twisted characters, you'll have a blast. If you're looking for a hack and slash game, you'll be upset with the result. Also, if you're one who doesn't like to perform side-quests, you also will find this game incredibly tedious, since most of the fun comes from talking to everyone and experiencing all the possible paths and people. Still, it's a game that everybody should play, without exception. It's just that good!
I guess the best way to advocate this game is by anecdote. I usually play games for at most 2 hours in a day, and that only on weekends. I installed this game on a Friday evening and within 36 hours I'd sunk 22 hours into Psychonauts to beat the game in two lengthy sittings broken only by a few hours of sleep. The addictive platforming, original characters, vividly beautiful world, and well-balanced difficulty curve make this a fascinating game that everybody should play.
