Here’s an article with tips on how to do really good presentations on your products and services. If it’s true, then at best, the average attention span for a presentation is 7 – 10 minutes, so why is the average presentation over 20 minutes long?
http://www.mrmediatraining.com/2012/08/23/how-many-minutes-is-the-audiences-attention-span/
As with many things a successful presentation is a combination of the medium, the message and most importantly, relevance. Powerpoint almost always defaults to a linear structure, and there is nothing inherently wrong with that, but it doesn’t suit all messages, how often do you find your skipping slides due to a one size fits all presentation. To produce a successful, engaging presentation you need to use the right medium to communicate your message. That’s not always going to be Powerpoint, or Prezi. It might just be something different.