It has yet to be tried. No, dictatorships or oligarchies are not communists. It also never will be tried outside of maybe 15 people
True communism actually seems like quite a good thing, for the people and species in general, especially when considering what is coming down the line for the globe as a whole (we have yet to actually see how ugly the food industry alone will become - extremely costly for anything good).
However, true communism is also all but impossible with current human mindsets. We absolutely cannot think like that, and I think, to establish and maintain a true communist state, we'd have to genetically modify ourselves to break past some of our shortcomings. We are, by instinct, far too territorial and tribal.
I think it COULD be possible, maybe.... just maybe... at a very restrictive level of governance. Specifically, a world government. We desperately need it, as a species, if we are to survive the test of time. Take the U.N. concept, make every single country represented equally at the world summit, initially share all government wealth and then keep it completely "communal." Countries become Provinces/Territories, and we are all united under a single banner. Of course, local government will exist, but the parties of the world can help craft and regulate (a United Earth Constitution?) local governing bodies.
It's also entirely likely that such a thing, the one thing we truly need (you'll see, as we become more globally connected, it's only going to get worse), will probably only be thought up, or at least only be possible, as a result of global strife and destruction.
With all these revolutions occurring around the world (thanks, entirely, due to social media and the internet in general), it does seem that the current picture of the world might not actually last all that long. Things are moving a lot faster than they ever would have.
Revolutions usually need a few decades to build up the fervor and "educate" enough people and get them to support your cause.
Based on history, the way of current trends, and how so many things are connected (in many ways)... I have no doubt the next 50 years are going to be rife with disaster all over the world... it'll be really interesting if any of that finds its way into our borders.