I think free movement between governing systems would do a lot to weed out some bad ones and make them all more competitive. Your big problem is of course geography - you couldn't, for example, allow tens of millions of badly governed people to migrate into a small country, as they would destroy what made it desirable. But if you could vote to put your physical area under the control of a more desirable government, that would be a great leveller. Imagine you lived in Darfur and you could vote for the Swedish government instead of your own. It'd be a bit of a pain for the succesful government to adjust to ruling a culturely, geographically, and economically different area, but in the longer run, well managed governments would probably benifit from the increased territory, population and diversity.