Today, ETH/BTC had a very good day. First of all, ETH gained substantial ground against Bitcoin, making ETH more valuable and desirable in the process. Second, and most importantly, ETH/BTC has broken out of the downtrend in which it has been trading since early December.
Ethereum is a more 'risky' asset than Bitcoin. If ETH gains against BTC, that means that investors become more risk-seeking. When investors are willing to take on more risk, this is always good for alts and the market overall.
Therefore, this break out might be the start of a new bullish (recovery) phase for altcoins.