Ethereum have designed a Turing-complete scripting language on the Ethereum network, which makes it much easier and convenient for programmers to actually start building programmable money. Through Ethereum, it is now possible to write Smart Contracts (programmable money) and that for any currency you wish, including Bitcoin.
So Ethereum and Bitcoin can be see as a couple that can strengthen each other. But Ethereum can exist and work entirely without Bitcoin . this is make it so special.