I don't always rate albums --- seems a little arbitray --- but when I do or if I have to, I usually use 3 as the basic "good but not overly great, sort of average" album and everything above that climbs in quality, with 4 bwing pretty damn good and maybe unexpectedly so, and 5 being the pinnacle, love this album, you have to hear it. On the other side, 2 is disappointing, mediocre, not really worth listening to and 1 is music I wipe my ahhh there you have my basic ratings.
Of course, there can be ones that fall more into one but less into the other so you can have half-ratings too, where maybe an album is say better than 3 but not quite a four, in which case (anyone?) it's a three and a half, and of course the other way too, where it's not quite that good but not quite bad enough to get say a 2, so it's two and a half.
Probably how most people run things I guess.