Although Bitcoin and Ethereum are both based on the decentralized blockchain architecture which has no middleman, Bitcoin is strictly a cryptocurrency. All transactions pertain to buying, selling and transferring the coins.
Ethereum's cryptocurrency (Ether) can be bought, sold and traded like Bitcoin. However, Ethereum is also a general-purpose platform that hosts other cryptocurrencies as well as "smart contracts" that are automated agreements. See smart contract
Both cryptos are having major impact on the world, but for different purposes. Bitcoin is entirely unregulated cash. Ethereum is also a store of unregulated cash but so much more because Ethereum can keep track of anything. It is even called "the world computer," as dramatic as that sounds. See blockchain oracle
Cryptocurrencies and Tokens
Although Bitcoin is the only asset on the Bitcoin network, there is no end to the types of assets on Ethereum. See Ethereum token
Cap and Speed
The number of Bitcoins will eventually top out at 21 million in the year 2140. Ethereum has only an annual cap of 18 million Ether.
A new Bitcoin block takes up to 10 minutes to become part of the blockchain. Ethereum blocks take only seconds. See Bitcoin