What makes a coin worth investing?
It usually is the underlying project idea and its utility in the market. ETH has utility as a smart contract and is widely being used to create cryptocurrencies, exchanges and other stuffs which means that it has potential to grow in term of demand.

Then comes the supply cycle. The supply of ETH is uncapped. But that isn't a problem because the release of tokens isn't that quick. Hence, the demand and supply cycle works nicely.

At this point, the whole market is suffering. But ETH can be a good investment at this phase.