Here are my thoughts:

1. Icon Design: The badgers in the Cornwall project are OK, fairly simple with a white border. If I was going to be picky I would say the should have used an outline of a badger and reduced the number of colors in the icon to two. Zakouma is a different matter, animals have been marked as colored circles, certainly simple but doesn't help differentiate them from one another and also requires viewing of the key to interpret. You should be able to guess what an icon is from the map without seeing the key.

2. Use of Lines: Doesn't apply in the Cornwall project, in Zakouma lines have been used badly, for example they should have chosen a different color for the track of the elephant than bright red and also turned this off when the file is first opened. Far down in the file you can find a white line that illustrates the track of the survey plane used to collect the data. This should be a dull grey so that it can be seen but does not take over the view so much. See the image left for an example which shows the track of a surverying boat in the ocean.

3. Use of color: The Cornwall project works fairly well although I would use a less bright green. However, Zakouma uses lots of bright colors which over clutter the view. It is especially apparent when the file is first opened as too many features are visible.

4. Use of Overlays: Zakouma does not have overlays, the ones in the Cornwall project work well and are simple.

5. Pop Up Design: Both projects have fairly simple design which works OK. Google seem a little obsessed with the design of Pop Up design (e.g. here), in my opinion its far more important to get the map designed well.

6. Introduction: The Cornwall project does fairly well on this by keeping things short and simple, however, if I was picky I would suggest they move the text from the folder and put it in an element that appears in the places column with the text 'Introduction' in the name somewhere. Zakouma has an introduction that is much too long and goes on into 3 sub parts. It just won't get read like that and also, the sub introductions deal with topics on how to use Google Earth, much better to provide links to Google's help with that.

7. Structure and Narrative: The Cornwall project doesn't really have a strong narrative as it is very simple in form. Zakouma is much too complex, it would have been better to split into into two parts with an introductory file with simple elements and an advanced file with some of the less interesting detail. It has far too complex a structure in the Places column.  The red cross in the image above and grey boxes within pop up boxes are caused by broken links within the file, the file should be removed from the web or these links fixed.

8. Have Users Needs been Catered For? I think by now it is apparent that I think the Zakouma project has failed in a number of serious ways , however, at its heart it has a narrative about a place that very few of us have or will visit which is where Google Earth can be extremely effective. By comparison the Cornwall project is much simpler but I am not clear about its actual purpose. Is it trying to promote the organisation as a whole by showing just how many sites it has or is it trying to help visitors with information about where to park and so on? It is not clear, both uses require slightly different Google Earth projects to make the best of the tool.

Back Story
My reasons for suggesting these two projects for analysis were not just because they are interesting, both have been promoted on Google's own site as being good examples which I think says something about the general lack of good quality Google Earth projects on the web. The Zakouma project is from National Geographic, to be fair it was published early on so can be excused some rough edges but I was surprised that it came from a magazine so famous for its wonderful design.