Well this statement is subjective and depends on individuals. I have seen people that has had much success stories with other coins in terms of Financial improvement than Bitcoin.
Well this maybe as a result of adoption. Many investors started believing in Bitcoin late and then the price had gone up. But those who still took the Altcoin route had success also.
I dont limit my thoughts on Bitcoin to finance, because its volatile like others but unlike others it serves a greater purpose and would also be essential in the future.
You are right, altcoin are profitable too but bitcoin has a real use case that it is believed will benefit its investors more in the long term. I believe in the potential of bitcoin, but I also believe that some altcoin can be held for the long term. The percentage depends on the individual, but if it were I'd probably be 70% or 80% there for bitcoin.