Ok, don't have time to read the whole thread right now, so forgive me if any of these have been mentioned. In no particular order, just as they come to mind:
1) The available races for PC didn't all look like various versions of Elves.
2) Elves were WAY cooler. Not the diagonal-eyed neutered wannabees they are now.
3) After comparing illustrations, not every monster in the 2E MM was on an extreme starvation diet. Back before 3E, monsters actually ate things. Wait, Xorn are actually eating more. They are the exception.
4) The PHB equipment lists didn't have silly pictures that looked nothing like what they were supposed to represent or just plain goofy (such as the "breastplate" illustration and others.

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5) The covers of the books actually made you want to play the game, not keep them "locked" up.
6) Halfings were, well, halfings. Who are these little tiny people running around 3E now? Oh wait, I remember, small elves.
7) No +34/+34/+29/+24 per round for a total damage potential of 200 points of damage...or more. My current 3E PC was consistently doing close to 20 points of damage per hit. At first level. With zero XPs. Without magic. As a cleric. Of a non-battle god.
8) Levels actually had to be earned....over time. A LONG period of time. Yes, that is a plus IMHO. I am still trying to understand how my current 8th level PC is still a 19 year old, not having aged a single year since he career started a mere few months ago. Back in the day, he would be middle-aged by now and looking like the the proper "lord", or "high priest", or what have you, should look. No acne.
9) No errata upon errata for the playtested (?) core books.
10) Lots and lots of good source material out there, mostly free.
11) Dwarves actually had a cool "anti-magic" niche to them. They were rarely magic using, but resistant because of it. Made them unique. Now Dwarven Wizards are everywhere and dwarves are just stocky elves.
12) Racial level limits. You heard me right. There is a whole world out there that has a history before the PCs arrived on it. Explain to me why a race that lives hundreds or even thousands of years doesn't have members walking around that are 90th level or more? At least the 1E/2E exponential XP charts and level limits helped to explain this somewhat.
13) No smack-downs. Especially the "barrel full of slugs" type.
There are more of course, but I'll stop at lucky 13 for now....it's getting late and I need to stop rambling. But let me say in all honestly that even with all the above I WOULD STILL NOT want to give up 3E. 3E is still a way better system overall. So let me just close by saying it weren't for 2E's mistakes, we wouldn't have 3E.
