For me it is ethereum, but it is just my opinion it depends on you what to buy. Besides I saw the value of eth and it is the most expensive altcoins if bitcoin cash is not included. And also I see a lot of potential in that coin because they will not reach that kind of value if they are not that good. They grow fast just like what bitcoins are before. But bitcoins are far ahead from them but if you are talking about altcoins probably get a lot of eth.