The first one for me, it's pretty much single-gamedly (heh) responsible for the creation & existence of Sorcerer's Place. I don't make it much of a secret around here that I prefer the original either. BG2 was way too cramped for me, with everyone and their grandmother wanting you to be their saviour and little freedom of exploration - you can't go 10 feet in any direction without bumping into a quest. I loved the exploration aspect of BG1 and I just hope that Oster & Co. don't stuff in a bunch of filler material into the more open areas. That'd just kill it for me.
I just want to play the original again, just in a proper interface for 2012. The inclusion of everything from ToB will already change the original way too much for my liking (call me a purist...). Ideally there'd be a switch to turn all the new stuff off to be able to enjoy both the original and the "enhanced" experiences separately. How about it, Trent?