just a few nights ago the three of us who live here took turns picking songs for a single "essential Pavement CD" and by listening to it we realized why they were the greatest band of all time (kinda). they just wrote such amazing songs. for all they are thought of as being "anti-rock", that's completely misguided. Pavement were a rock band. and Malkmus can play extremely well. listen to the guitar work on "Fillmore Jive" or "Rattled By the Rush" or "The Hexx".
and when they weren't being an awesome rock band, they were an amazing pop band. from "Box Elder" and "Perfume-V" to "Shady Lane" and "Spit on a Stranger".
mix in some amazing ballads ("Here", "Newark Wilder", "Major Leagues") and some leftover punked-up numbers ("Conduit For Sale", "Unfair", "Serpentine Pad") and well... that's what the big deal is.
if you don't like them that's cool though. i just think it's easier to make the case for Pavement than for, say, Slint or My Bloody Valentine, and those bands having much less recorded material is only part of the reason. Pavement are pretty close to objectively good at being a rock band.