The story is well written, and the game is chock full of side quests. Unlike most games however, they aren’t just lame fetch quests and filler to pad things out. There are dozens of well developed, lengthy missions that often chain together into questlines that would be the main story in other games. The game is at 80-150 hours long, depending on how much of a completionist you are.
The companion NPCs often have lengthy loyalty quests, and banter between each other (and other NPCs you meet.) This alone adds tons of replayability, especially given the wealth of missions in the game. Minsc and Jan are some of my favorite characters to this day.
The graphics, to me, look like a beautiful painting. The spells have varied, wonderful effects, and enemies explode into gibbets if hit with excess force. I considered Bioware’s next game, Neverwinter Nights, to be a massive downgrade in looks when it first came out, and that’s even more true today, as most early 3d games aged poorly. BGII has aged like fine wine in comparison.
Most RPGs have tons of trash mobs. Generic, nameless filler for you to wade through. While BGI had these, BGII for the most part doesn’t. Most enemies have names, or are interesting monsters that need to be fought differently (Trolls have to be killed with fire, beholders have rays that can mind control or petrify your party, and are best reflected, or dealt with via summons, Mind flayers are terrifying to anyone without protection from mind control, and even those with it, etc.) They take strategy to deal with, drop unique loot, and often can be reasoned with, or at least talked to. It makes the world feel real to me.
Items: I’ve never seen a game handle items quite like BGII. Using the D&D system means that there is a sharply defined scale. Enchantments go from +1 to +5, and while there are a few generic items (Eg: +2 sword), there aren’t ANY randomly generated ones. Most items have detailed backstories, and feel and look unique, with great animations and abilities.. The effect of this (and the stat system, which are virtually impossible to increase, and only go from 1-25), means that many items are useful throughout the game.
That awesome flaming sword you picked up with the cool backstory? Useful throughout the game to finish off trolls. You’ll want to keep helmets of charm protection around to deal with beholders and mind flayers. There are a few anti-undead weapons that you should keep (and upgrade) to deal with vampires and liches, and so on.
On top of this, artifacts and high end items (that you make or find) truly FEEL like a signification upgrade. The limited stat range (which you don’t improve by leveling up), means that items that increase them feel far more impressive than those is say, Diablo. Finding boots of speed lets your characters race across the screen, saving time and making them far more flexible in a fight. Making dragon scale armor from the corpse of high-end bosses is immensely satisfying. But you’ll still likely find occasional uses for earlier items, which makes the bags of holding you find useful!
The magic system is increadibly satisfying to me. While low-level wizards are a bit weak, high level ones make you feel like an archmage. There are numerous spells, which are limited in use per-rest, which means you can’t cast them as much as in most games, but they’re a lot more powerful.