This is presentation by Appistry is a decent, 20,000 ft. level view of why cloud is a game changer. I don't know that I would put Cloud computing at the level of impact that the internet had, but I do believe it provides the world a better platform for computational capabilities and is a necessary (or at least valuable) step in the evolution of computation.
To me, Cloud computing is similar to a stage in the evolution of utilities. Electrical power, in the early days, was generated by the user with complex systems (relatively speaking) required to make it happen. Today, electricity is ubiquitous (essentially) and using it requires you simply plug a cord into an electrical socket. The entire user environment has coalesced to work with the electrical "cloud". (e.g., appliances have been standardized, backup systems have been developed to ensure it is (almost) always available, etc). Computing is in that same evolutionary trend where (when we look back we will realize) it really hasn't been easy to get an additional "unit" of computational power (e.g. the next application). You had to have a computer, get the software, set it up, and run it. Smart phones has changed our view of getting this extra unit of power and has wet our appetite for Cloud. Cloud computing takes computational capabilities one step closer to ubiquity by bringing computation and applications closer to the end user. It gives us more software options, software that is already running and a bigger environment to run applications. Cloud promises additional capabilities such as standard metering, connectivity standards, and management software so that it is always available with many of the complexities hidden from the end user.
So, going back to the premise, Cloud does (will) bring us one big step closer to a more ubiquitous environment for computing. Turning computation into a "utility" is going to change our lives forever.