Are all political systems equal, meaning they bring out the goods that we all want in our society, when ideally practiced, or some would necessarily come out better than others just by the fact of their nature, arrangement and constitution? For instance, I once held the belief that communism is an equally good way of a government as democracy if it is ideally practiced, but I now doubt this point of view. Do I have good reasons to doubt it?

You haven't told us your reasons for doubting it, so that's hard to answer. But neither "communism" nor "democracy" is a sufficiently well-defined concept to be of any use for the important question you want to raise. First, it's essential to distinguish between the historical governments that described themselves (or were described by others) as "communist" (or whatever) and what "communism" might have meant before or after that as an aspiration or a political or social ideal, or even just as a description. These are entirely different things and often have no relation to each other at all. Second, there is the question about which features of a given society "matter" in the sense that they actually characterize how the society "works," i.e. that they influence other parameters in a society and determine what happens in it, how people are treated, how rich they are, etc. Insofar as we know anything about this at all, such outcomes generally have little to do with the extremely crude terms generally...