This is a very well-maintained hotel in a good location in Piraeus. It is a convenient walk to the metro that takes you directly to central Athens, as well as to the tram to Glyfada. If you are going on a cruise, your room may overlook the cruise ship and, again, the distance to the terminal is convenient.
The breakfast is certainly ample enough, it cannot compare to a similar hotel in, say, Germany, Sweden, or Denmark. Then again, that is to put too high a bar in the comparison.
It it listed as five-star. I fail to see the difference relative an ordinary four-star hotel. The main effect of the additional star is to bump up the per-night tourist tax.