OK - those are strong words, and there really has been a lot of great writing in the last 50 years (I did say "possibly"). But the combination of imaginative genius, over-the-top humor and just enough philosophical thought makes H2G2 a true standout. The radio plays predated the published books, and were my first exposure to Douglas Adams in the early 1980s - they remain the best way to experience The Hitchhiker's Guide.
There are only a few audio books that I return to and listen a second time. H2G2 is an audio book that I am moved to listen to at least every two years. Basically, I'd be lost without the Guide... If I could give it six stars, I would.
P.S. Years after I fell in love with the books, I learned that Adams had been a script writer and editor for the BBC's Doctor Who, and that he was a friend of Richard Dawkins - he introduced Lalla Ward (who played Romana on Doctor Who) to Dawkins, they subsequently married. Lalla Ward co-narrates Dawkins' audio books, which I also recommend. That serves to illustrate "the interconnectedness of all all things" (which is something you'll come upon in another of Adams' books - Dirk Gently's Holistic Detective Agency.
See my review of "The Primary Phase" for my glowing - nay, gushing - endorsement of the H2G2 radio plays.
This radio series starts at the offices of the Hitchhiker's Guide, where something is definitely amiss, and ends with a visit to the ruler of the universe - an old man, who's trying to feed his cat a bit of fish. It's as wild a ride as the Primary Phase, and was broadcast beginning in December, 1978 (months after the Primary Phase had been broadcast).
Really great stuff!
I don't think it could really fit into canon, but it feels like a “real” Doctor Who story because of course you’re hearing the Doctor’s voice and vocal mannerisms. Tennant does amazing impressions of the accents and speech patterns of Rose, Jackie and Mickey, and he creates other voices for other characters. On top of that, you get the narration in his gorgeous natural Scottish accent! The story was cuter and sweeter than most episodes but there were some good twists and exciting moments.