I know lots of ICO are not so successful and that affect the price of ETH but Bitcoin is slow among other disadvantages.
Then why ETH drops so low but Bitcoin can stay such strong recently?
Bitcoin has a lot of advantages too, the main one being that it's the most widely accepted, most widely traded cryptocurrency.
And you are missing a disadvantage of Ehereum: Ethereum is an altcoin. That means [1] if people want to sell, most probably will sell for Bitcoin then sell the Bitcoin, giving some more satoshi to Bitcoin economy, which, bit by bit, do count; and [2] traders know that altcoins are higher risk investments than Bitcoin and they liquidate more altcoin positions than the Bitcoin ones.