Santiago, just for a number of animations removed. Just from the first 2 days.
Gabriel doesn't climb the ladder like he could in the original. He doesn't sit down to use the type writer. Majority of the tourists in Jackson Square are gone. One band is gone, and the other two bands are missing at least 1-2 band members each.
The majority of the random uniformed officers in the police station are missing. The only one left, just stands there, and doesn't go about his business.
At the crime scene about 2-3 uniformed officers are removed, in the original they were doing things about the crime scene like checking the ground, taking photos, taking notes etc.
The body is completely covered in the original, and Mosely would bend down and uncover it to show Gabriel. Now in the new one the body is uncovered throughout the entire discussion, and is covered and taken away offscreen (or rather in a cutscene).
On Day 2 the 'electrician' doesn't show up in the police station. Again the various random tourists don't show up. This includes a woman and son, an old man, red-haired woman, jogger, etc. The jugglar doesn't show up on later days.
Obviously since you can't get into the voodoo place on day 1, the 'girl' volunteer who runs the shop on day 1 is not in the new game.
http://gabrielknight.wikia.com/wiki/The_Girl Also note almost every new close up scene in the remake, replaces what were represented by a number of different character animations in the original. For example all the books in the bookshop were scattered in different sections of the store, and there was an animation for each one, either Gabriel stretching to reach high ones, or bending over to reach ones on a lower shelf. But since it goes to a close up there are no animations whatsoever. They moved all the books to a single spot (this also removes a number of descriptions that were originally found in the book store as well).
This is not a review. But I've been playing both the original and the new one side by side making a list of as many of the changes from day to day. Including list of characters, that show up, and incidental animations.
[url=http://gabrielknight.wikia.com/wiki/Gabriel_Knight_I:_Comparisions_between_the_original,_20th_Anniversary,_and_the_Novel#20th_Anniversary_Edition]http://gabrielknight.wikia.com/wiki/Gabriel_Knight_I:_Comparisions_between_the_original,_20th_Anniversary,_and_the_Novel#20th_Anniversary_Edition[/url]
As for anyone interested in general comparison of each screen, the new in-game behind the scenes offer that feature. You'll notice most of the old games went more for a dark cold look, while the new game went for bright and sunny.
A couple of reviews that covers many of the games weaknesses compared to the originals (including atmosphere, and missing assets) can be found here;
http://www.rockpapershotgun.com/2014/10/15/wot-i-think-gabriel-knight-20th-anniversary/
http://www.hardcoregamer.com/2014/10/15/review-gabriel-knight-sins-of-the-fathers-20th-anniversary-edition/111907/
Another major weakness compared to the original is that in the original you could could look at a dozen or so items on the screen and get a description and there were many more extra ways to interact with the things on screen with the games many different command icons. However, the remake removes most of the extra commands, and limits which ones you can use on any 'hotspot'. Each room is has been limited to a few hotspots on screen, maybe 1/2 to 2/3s of what could be interacted with originally. Some of the descriptions are completely missing, or replaced with descriptions of something entirely different. Or completely wrong, Cazanough's house for example a painting on the left wall of the remake mentions it being a portrait of a woman in old style clothes, but if you look at the actual image in the game, its actually a scenic painting. However, in the original game it was a woman in old style clothes (so the description in the new game would actually fit the old game, but not what actually appears on screen). Some of the best descriptions from the original are simply missing. Also many of the things you could look at in the original, have been simply removed from the scenes altogether, for example the mess of Mardi Gras beads in Gabriel's bedroom, which leaves the new scenes looking a whole lot cleaner than in the original, than the cluttered mess. But also less interesting in the process since there are fewer things to look at.
Also keep in mind I don't think the new game is 'terrible', it just suffers from weaknesses compared to the original IMO. It is overall a 'good' game. I just consider the original better, and a true classic.
Its incidental trivia, but I also came across an odd continuity error in the cash register in the book shop, the money is of the 1999-2003 'fat' historical figures, rather than the older style money that was actually used in 1993.