God, I wish we could have a discussion on Muslims and Al-Qadim. The Anthropology Major in me is just rearing to go.
Now, onto the question at hand...
I happened to buy a 2e PHB today at a huge booksale (done every year, where you can buy hardcover books for 3$!). I got my PHB for three bucks... and I started leafing through it in the lineup. One thing caught my eye: in one of the examples of play, a character falls into the ocean and has to swim to safety. She makes her checks according to the rules given... and then, in the example given, we see the GM making up a modifier on the fly to represent choppy water. This would be a no-no in 3e (they'd make sure the example used a situation covered in the rules), and 4e would give us a nice bit of guidelines for GM adjucation which were essentially a set of rules to follow. 2e just said "DMs, make up rules as you need them", and left it at that. And I gotta say, I appreciate that.
Another observation of the 2e PHB is that most of the art is based around solo heroes. A wizard does stuff to surprise villagers. Another wizard polymorphs a unicorn into a dragon. A fighter is about to burst into a tomb. And so on. The examples do the same, with many focused on one character, or smaller groups. Why? I think the goal of 2e, as compared to 1e, was the development of story-based roleplaying.
Other editions were more "GMs make a map of a place, and PCs interact with it" as their assumed framework of play (every edition's DMG but 2e's had a big section on dungeon creation). 2e, instead, was more about worldbuilding and plot play, in the general terms of the implied setting.
It's a playstyle shift, and I think that's why people's opinions of the game vary so much. If you were a GM first and foremost, odds were good you had fond memories of 2e, because you had a lot of power and the game was built with you in mind. If you played 2e, you may not have liked it as much.
Personal theory, there. I could be wrong, and I probably am.
I loved 2e, and I still have a warm spot in my heart for it. That being said, it's pretty messed up in some ways. Many of the rules are not exactly useful, and at least a few times, there are two different (and perfectly legal) ways to accomplish the same action.
As an example, saving throws.
You could, in the rules as written, require a character to make a saving throw to dodge an effect, or require that character to make an ability check. If he had to to a saving throw, his chance of success was dependant on level (as saves improved over levels). If he had to make an ability check, it was not dependent on level (as abilities barely increased over level - only through the use of Wishes and play possibilities).
As a GM, then, I could modify things to fit my group. If I want that porticullis to slam shut before the PCs can reach it, I can force them into making saves vs. Breath weapon if they're low level, meaning it's unlikely a PC could make it... if they're high level, that same situation could be covered by imposing an ability check with a small penalty. It was a beautiful dichotomy that could allow the GM to influence the course of the game while keeping the rules of the game out in the open.
the classes in 2e were cleaned up a bit compared to 1e - the bard is now a class (and pretty powerful, too!), the ranger was weakened a bit, and the druid had a nice re-structuring. Thieves were made into one of the most interesting classes in the game - in my experiences, theives were the most frequently played class in 2e.
Kits were generally garbage, though the books were still an interesting read, and often had some great campaign ideas. the campaign settings in 2e were the best, as others have mentioned. I still sometimes think of re-starting a 2e DARK SUN game...
THAC0 is messed up. Weapon speeds were confusing. Surprise was a bit odd. 1 minute combat rounds never sit well with me. Prime Requisites strike me as unfair for unlucky players. And there was very little reason to play a human in the game (unless you KNEW the game was going on for years).
But still, it's a great game, and worth checking out!