For the most part, I review albums that I like. Occasionally I will review a bad album: 1) If it was by an artist who I previously liked material from and was therefore disappointed or 2) if it is an album that is notably bad but is receiving high ratings (particularly if the current reviews are shit/vague/moronic).
I listen to mostly black metal and technical/brutal death metal, with the occasional folk, funeral doom, and power metal.
When I review an album, 70s means it is "good" but not "great", 60s means above average, but barely. Anything below 60 is some varying degree of shit, ranging from mildly tolerable shit to very, very extremely shit.
Anything 80% or over is very good and is recommended. If something is in the mid to high 80s, it very probably exists somewhere on my best of the year list. Anything 90 or higher I consider essential to the (sub)genre and likely top 5 of the year.
My favorite album is a 99%. Until I hear a perfect metal album, and I haven't yet, I won't be giving any 100%'s.
Finally, in the absence of a polite way to say this:
To all the idiots I see with half of your reviews giving 98s, 99s, and 100s, I say this: You are clueless, ignorant fuckwads and you wouldn't know musical taste if it hit you going at relativistic speeds. You ruin the integrity and consistency of reviews on this website, and perhaps most importantly, you have absolutely no fucking idea what you are talking about.