Many altcoins are created with different purposes. I am not sure why only Ripple is being compared? In reality, altcoins shouldn't be compared with Bitcoin at all. There are multiple reasons alongside centralization. Also I am not against altcoins. There are many benefits altcoins provide.
Bitcoin is more like pioneer in this market and enjoys the first mover advantage. But altcoins are also needed, especially coins like Monero. In this world of surveillance, privacy coins are really beneficial.
No altcoin can be compared to Bitcoin. No matter how well a centralized coin does, it will never gain the trust of investors like Bitcoin. Bitcoin is very popular and investors around the world trust it blindly. Because everyone believes that no one can control Bitcoin and Bitcoin will never be a scam. But centralized platforms can scam at any time for any reason. Many popular coins have been seen crashing in the past and popular exchangers have been seen going bankrupt. So no other coin can gain more trust than Bitcoin. So no other coin can be compared to Bitcoin in any way.