I think there is no crypto currency which can replace Bitcoin, at least in our nearest future.
The most successful and valuable altcoin right now is Ethereum, but it is far away from replacing Bitcoin despite its high potential and value.
Bitcoin will keep its first position on crypto world for several years, most likely.
You're right. At least for now, bitcoin would be the one dominating the market because it is the cryptocurrency that has the most supporters. Although its technology is what we say the most basic in terms of blockchain technology and it has many flaws, still it is the most famous of them all and people still want to accumulate it and make it as their long term investment.
Maybe one day, like ethereum will be able to get as much supporters as bitcoin then it will be the one that will dominate the market. It has the highest price as well so people especially the newbies wanted to get a share of it. Bitcoin also has cards so it is easier to use unlike other cryptocurrencies.