i happen to think that's the ideal government. it requires a dictator with the right qualities, and they are rare. Thus, what is possibly the 2nd best government type: democracy.
The problem, of course, is that what is considered "benevolent" is entirely up to the dictator to decide. That alone makes it a non-ideal government type.
No, it is up to the coherent extrapolated volition[1] of the dictator's people. (At least, it seems like a good guess.) What makes a government less than ideal is its failure to apply that volition. The question then is how hard a given type of governance is likely to fail.
Now I agree that for a host of reasons (like taking one's own volition for the country's CEV), dictatorships do not rank high.
The point of a dictatorship is that the people don't have a say. The dictator does what he wants and portrays himself as benevolent through state-run media.