This post should probably go to AD&D section, but since I learned what AD&D is by playing BG1/2 (and the only other CRPG that i enjoyed almost as much was Realms of Arcania series, btw - anyone played that one? - and it used a different system) - i thought what's the heck.. Where else do i get valuable feedback after all?!
Ok, so i'm gonna talk a bit about
magic in BG world and since it is very much based on the AD&D magic rules i can't help talking about it too.
I am not going to say all over again that
AD&D is unrealistic, since it's a major separate topic which can probably be covered in some 500 pages tome only. There is no argue that AD&D defines its' own world that only slightly resembles reality, which may be "cool" for certain purposes (i
do enjoy playing BG after all). What troubles me the most is that in this wonderfully created AD&D (and BG) world there are certain inconsistencies, mostly of magical nature.
(A side note on the "realistic" side. It would be probably possible to model things (read - combat & damage) quite realistically if we model each character or monster as an object containing other objects, not only such as legs and arms, but also heart, lungs, blood vessels etc. With this approach a person with his heart pierced would die instantly or would drop his sword if someone cut his hand off. I am actually thinking of giving this as a small OO programming assignment for the students, since it would be both a good illustration of OO principles and also useful simulation. Will let you know if i do

And of course there are limitations to using this approach in real games because of very high computing power requirements. However, we all know how fast the industry develops. I might elaborate on this later.)
Ok, getting back to magic. I think even for the world that does not try to closely model reality, AD&D still pays too little attention to physics. Because of that, several nice creative opportunities are missed.
So what am i trying to say here

They introduce the notion of "magical energy" that can be used by magic users to produce different effects, and here is where the first inconsistency appears, namely
magic resistance and saving throws. I cast a fireball, which supposedly creates just that - a ball of fire which explodes. Something like Molotov ****tail bottle. Ok, but if that nasty demilich is 100% magic resistant my fireball does absolutely no damage! Hewston, we have a problem. Logically, the demilich must throw save vs fire and apply any modifiers to damage taken based on that. But what we have here is magic resistance influencing real world, physical object - a ball of fire! You may say - this is not a real ball of fire, it is "magical-energy-based" ball of fire. Heck, don't call it fireball then. Call it "some abstract illusionary thing that deals damage only in your imagination, which is then subconciously applied to your physical state". Let fireball deal not 6d6 fire damage, but 6d6 some magical energy damage. The same with cone of cold and all the other spells which supposedly create
real-world objects.
If we even accept that it is some magical energy, not the real fireball, then we have to agree that magic users have no real influence on the world around them. Sure, magical energy deals damage, but it's still some kind of illusion - magic resistance et voila. And that's where the lost opportunity is -
allowing magic users really alter the world around them. Create fireball that is not resisted by magic resistance but by asbest clothes only. Lightning bolt that is really a bunch of electrons piercing that evil heart. What magic resistance has to do with that? One can save from that disaster, but not by means of magic resistance, but as with any other real world object. In this case, by wearing rubber suit or something

I can continue a lot, but i hope you got the idea.
Now, time for a
nasty nuclear physics type spell 
. You might be familiar with Einstein's most famous formula, E=mc**2. This simply means that if we convert all the mass of any body to energy, we're gonna get REALLY lots of it. Small nuclear bomb (around 10-20 kg of active mass) utilizes less than 1% of the above formula and deals you know how much damage. Now, time for combining magery and physics

Let's say a magic user (very high level indeed) mastered the way to trigger chain reaction that converts mass into energy in the stones lying all around by channeling lots of magical energy and forming it in a specific way. Well, you can imagine the consequences... That magic resistance will save that demilich no longer. But, there are some cool opportunities to counteract this. Like one nasty mage is trying to trigger chain reaction in a small stone right at the feet of his opponent. The opponent at the same time, wishing not to be evaporated, channels his magical energy and tries hard to keep the atoms together in that stone... Wow!
There are of course many more implications if we think of the ways to combine physics and magic, which open wide possibilities for enhanced gameplay experience. There is also another issue with AD&D magic which i'd like to talk about, but i definetely should stop in this post already!
Cheers,
Rentgen.