The closest analog I could come up with something like a baseball card with an authenticated signature of the player. Yes you could copy the baseball card, and even the signature, but I have the original, and it's been authenticated by by a third party expert.
In this case, the card is an image file and the third party is math (the smart contract that issued the token).
Sentimental value is based on sentiment, so you probably shouldn't try to apply objective logic to something that is subjective to every person and expect useful results.
> In this case, the card is an image file and the third party is math (the smart contract that issued the token).
There's no canonical block chain. So the same image can be resold on any number of blockchains and every buyer can claim to be the "owner" with the same legitimacy. Which is zero legitimacy. There's not even a meaningful way to verify the person selling an NFT had any rights to do so.
With a signed baseball card if you have physical possession of it then you're the owner. You have exclusive control over access to the card. Even if the card's inflated value drops because no one is willing to buy it, you still have a physical card to enjoy.
Sure there is. Anytime someone says "NFT", they are almost certainly referring to an ERC-721/777[1] token on Ethereum. What other blockchains support NFTs and have any kind of use?
Re legitimacy: how do you prove that any piece of artwork for sale in the real world is legit (the seller isn't violating someone's copyright or selling something stolen)? With an NFT at least, there's no such thing as a fake bored ape; the contract address that defined those is known. You can copy the image, you can even mint it, but it will be a trivially differentiable from the original, since it will belong to a different contract.
It's more of you own a receipt issued by a certain authority that backs your claim to the collectible item but not the item itself.
As with regards to sentimental value, I'm actually in favor of the concept in this context of collectible trading but I hardly see any application in the NFT world like for example yesterday someone posted an article about an NFT built atop Dorsey's debut tweet on the platform that plummeted a whooping 99% in value and the investor lost around $3 mln on his trade, that made me think what sentimental value could this tweet for him to warrant such a ridiculous valuation but I couldn't find an answer except it was just a vehicle of speculation for him, a very risky and foolish one in the end.
Please note that I use the word owing very liberally here