Without bitcoin every coin in this market is an altcoins. So ethereum is also an altcoins. But ethereum is the highest market cap altcoins in this market. You can go for any coin if you know about this market and you know how this whole market works. It depends on you if you are new to this market and don't know too much then go for big cap coins like ethereum xrp ada eos many more. But of you know how this market works you can go for any altcoins low or mid cap.