Compare has a definition, it doesn;t have different meanings to different people, that is why we have things called dictionaries, to eliminate issues with word comprehension. You can compare anything to anything, doesn't mean it is a good comparison though, it would depend on the person making the comparison to set forth a set of circumstances in which things are similar.. What Carmack said doesn't leave room for interpretation, Comparable means that two things have enough features in common that they can be compared to one another, and his meaning was clear that in terms of power the PS4 and X1 are similar. Someone may agree or disagree on a variety of factors, but it doesn't change the meaning that was originally put forth.
Things like this...
..do not leave room for interpretation.