Inspiration for great presentations
There are two aspects to your question, in my opinion: design and function.

Function. Many have criticized PowerPoint and bullet points and perhaps none so much as Edward Tufte in his essay booklet The Cognitive Style of PowerPoint: Pitching Out Corrupts Within. The defaults of PowerPoint and reliance on bullet points is interesting and "forces" users into a particular form of presentation where bullets are more reminders for the speaker than the audience. From this background an alternative is to use the so-called Assertion-Evidence Structure which takes a very different approach to building slides. 

In the Assertion-Evidence Structure the heading of the slide is the main point of the slide, a take-home message. The slides use graphics extensively to support and high-light the main point. The structure has been shown to yield significant improvements in both audience understanding than normal bullet-point presentations. Se the linked example of the structure.

The Assertion-Evidence slides are not necessarily pretty but they do the job very well so that brings me to the second issue.

Design. When you look at designing slides it is probably easier to list the don'ts than the do's. In general, anything "fancy" easily becomes boring when overdone. Therefore simple is better. I would also add that subtle is better. Do not use strong colours and avoid backgrounds that can clash with the text, either structurally or in terms of colour, after all you want your message to shine. 

So design anything with a principle to do as much as possible with as little as possible and you should be on a good road. I think referring back to Edward Tufte is useful also here.

So taken together, it is not clear what is a well designed presentation depending on whether you are looking at aesthetic impact or factual impact.