Overrated!
Why? I truly wish I knew..
For me, Baldurs Gate, when it just came out, was quite the disappointment.
Not only did it seem like computer games were thrown back a century as the graphics looked truly horrid.. (a static rendered world which looked basically the same as any interactive tile based one), but the combat system was clunky and a complete nightmare to boot. That is, if you actually wanted to employ some strategy. Yes, it did have the much promoted D&D rules system, or whatever, but for people, like me, who were pretty much used to Computer RPG's, this addition wasn't exactly the Holy Grail (more like an inconvenient study). If anything, it made everything feel like a carton board game with complex dice rules instead of giving an immersive experience like RPG's such as the Bards Tales and Wizardry series.
Also, the Experience Cap prevented you to develop the epic hero you were trying to become (unless you waited for -and bought the next EP). Obviously a marketing scheme instead of a valid excuse to level the gameplay. Made quite clear by the fact they only developed ONE EP (Tales of The Sword Coast).
The only redeeming point I can find (and that goes more for BG2 than BG actually) is the story and characters. Some of the characters are really memorable/funny, like Minsc and his pet boo, Xzar, and some of the NPC's you encounter. They have some of the funniest lines ever heard in an RPG as far as I know.
All in all a very mediocre RPG that got extremely lucky.
Oh and I almost forgot, even though BG likes to give the impression 'one can play either as a good or bad character, the reality is that there isn't a choice at all, since evil characters are so extremely handicapped that it's impossible to survive for long with them. Goody two shoes, or Neutral, is the only way to go.