NPR recently posted "Our Unscientific List Of Least-Known Fiction Winners" for the Pulitzer and it's a solidly least-known selection. I've only even heard of two - Cozzens' Guard of Honor (which I own but haven't read) and Guthrie's The Way West (have a copy of his The Big Sky). Of the rest there are only five authors with names recognizable to me. (Cozzens of course was the recipient of Dwight Macdonald's withering essay that almost completely demolished his reputation - more effectively than Twain's famous attack on Cooper did. Some have argued recently that Macdonald was working more from political than aesthetic motives, not quite addressing whether that matters.)
It certainly would be a worthwhile project to read all of these, in fact to read all the fiction winners in order. I'm not about to do that but how much of this really does have any kind of lasting value? Or did they benefit from the mood of the times, behind-the-scenes manipulation, locked juries or any of numerous other causes. McCarthy's award for The Road--generally considered one of his weakest works--is often viewed as really being for his career and not that particular work. In the notorious Ellington and Pynchon cases the mechanics of the Pulitzers came straight to the front but most of the time even the names of the jurors tend to be obscured. (If they're on the official Pulitzer site I can't find them.)
Since they're so high profile the Pulitzers are easy to attack but the track record isn't really that bad - maybe not as substantial as the National Book Awards (or adjusting trans-Atlantic-ly the Bookers) but certainly far ahead of such continual embarrassments as the Oscars or Grammies. Some of these forgotten titles likely deserve to be forgotten but I bet it's likely that quite a few of the older ones aren't even available in many public libraries due to their generally aggressive policies of thinning their collection (university libraries tend to take longer views). But hey isn't the Internet going to cure all this?