it depends on what you have in your head when you say "alternative to bitcoin"?
literary anything that is not bitcoin is called altcoin which is short for alternative cryptocurrency. so yeah all the coins you listed plus about 1700 others are alternative to bitcoin.
But OP here is describing in his thread the "top 6 crypto alternatives to btc" and not just merely alternative to bitcoin itself. Even though that is the case, this list was merely based on his subjective point of view and is not based on facts(since he didn't include his' source for it).
Many people believe that the top 6 cryptocurrency alternatives to Bitcoin are: Ethereum, Litecoin, Monero, Stellar, and Vechain Thor. Do you agree?
I agree that coins listed here(specially the ones I marked in the bold) really deserves to be called top 6 cryptocurrency alternative to bitcoin but where have you got the data for this? If possible, please include the link of your source.