a great album has two main attributes:
- a bunch of great songs
- those songs are in an order that brings out the best in them
some albums suffer from a weaker second half, or feel generally bloated, or lack internal variety. i think you ideally want to both start strong and end strong, because a huge part of someone's memory of an album is determined by both first impressions and by how it wraps things up.
for me, a 10/10 album has zero flaws. every song is great and the order couldn't possibly improved. it feels cohesive while also containing enough internal variety to stave off monotony. some good example are Rumours by Fleetwood Mac and Bridge over Troubled Water by Simon & Garfunkel
a 9/10 is almost perfect, but has one or two flaws. maybe a particular song is a lowlight, or maybe the whole thing feels either too repetitive, or it lacks cohesion. a good example is Thriller, by Michael Jackson. it's almost a perfect album, but i think it's dragged down a bit by the embarrassing, low-energy, and cheesy duet "The Girl Is Mine"
an 8/10 is a really solid album. i'm completely happy to listen to it over and over again. it likely has one or two really really great songs, and then the rest of the songs are good but not great. it might feel repetitive, or a bit bloated, or ends unsatisfyingly. good examples are "Hot Fuss" by The Killers (which has two incredible songs, "Mr. Brightside" and "Somebody Told Me" and then a bunch of pretty good songs) and All The Pain Money Can Buy by Fastball (similarly, it has the two highlights of "The Way" and "Out of My Head")