Here's a rather obscure one: "Wizards" (the 1977 Ralph Bakshi version). I saw it in a double-feature with Phantom of the Paradise (another obscure film) back when it was new. It's animated, some by hand and some by rotoscope. As with "A Boy and His Dog", this might not appeal to everyone.
I'm not actually sure that this qualifies as best, but I found it very different and intriguing. I love the ending too.
It's a pretty standard good vs. evil plot. Humans were all exploded in (what else? a nuclear war) and ancient races have come back to populate the earth. The respective good hero and evil antagonist are twin wizards, one trying to save the Earth and the other, destroy it.
"The Chrysalids" by John Wyndham, 1955.
The story is about a young lad growing up in a community in Labrador, Canada, one of many pockets of human culture several hundreds or thousands of years after a devastating world-wide nuclear war. Their society has re-invented stationary steam power and guns, but cannot understand the mutations to their crops, animals, and humans due to radiation still drifting from the south. Their religion is very strict as to destroying or sterilizing and banishing mutants who do not fit the definition of what is 'proper'. Some of the youngsters develop telepathy but must keep it hidden lest they too be judged as mutants. Salvation comes from New Zealand whose people escaped most of the effects of radiation and were able to recover technology much sooner.
John Wyndham writes a very interesting story around small community religion, politics, bigotry, heresy, and human nature. A good read.
Arrggghhh -- this is one of the ones that "popped into my head" while I was writing the blog and then it popped out again when I received a non-maskable interrupt (like my wife calling :-)
But you are right -- this was a fantastic story...
Two more post-apocalyptic tales by John Wyndham were "The Day of the Triffids" and "The Kraken Wakes" ... I think I will re-read all of these when I've caught up with the current pile of books I have (a) on the go and (b) waiting for for me in the wings...
Have to look for "The Kracken Wakes", and my ex lent away my copy of the "Triffids". I had to wonder in the Triffids when they were holed up on the farm behind the electric fence why he ran a gas-powered generator rather than salvaging a bunch of automobile batteries and wiring them in series to power the fence. Then they would only have needed occasional charging from the generator for leakage. Other than this, good story.
Other post-apocalyptic suggestions are "Farnham's Freehold" by Robert.A. Heinlein, and "The Songs of Distant Earth" by Arthur C. Clarke.