Good point. Only the OG Mons Lisa has real value.
There isn't only one painting ever tho.
Starry night, last supper, the scream, anything Dali or Worhol.
Other painting have value any worth in this comparison as would other blockchains.
Discussion
True. But if you ask someone what's the most famous painting in the world, I guess the answer would be M L.
It's just an analogy anyway, and all anologies eventually fail.
However, what the altcoins promise you is that they are 'like Bitcoin, but better', in whatever carrot they dangle in front of your face.
But that promise comes at a cost.
It cost you the perfection that Bitcoin offers.