It kinda is, everything falls on that scale, either people are being represented and representing themselves or they aren't. Everything else is just the mechanics of that.
"Many forms of Government have been tried, and will be tried in this world of sin and woe. No one pretends that democracy is perfect or all-wise. Indeed it has been said that democracy is the worst form of Government except for all those other forms that have been tried from time to time.…"
It's the main criterion. If the system doesn't last, then it's shit regardless of what it is. The main purpose of the government (and any organization, for that matter) is to exist for as long as possible, everything else comes second. I wonder what other criteria do you have in mind?