I am not bullish on Bitcoin. I think that there are at least 10 other coins out there that have significantly improved on the protocol. However, my opinion doesn't matter. People trust in Bitcoin because it's been around the longest and has a good track record. Ethereum is the same way when we consider smart contracts.
People trust Ethereum because it has a long track record and is the most developed. There are a quarter million developers working on top of the Ethereum blockchain. Ethereum isn't going anywhere. ERC-20 ICO coins lock into the platform. There is a lot of incentive for them to stay right where they are. It's true, Ethereum is having scaling problems. This is why I think that trickle-down theory is such a valid economic model when considering the cooperative nature of open-source projects.
Ethereum's glass is full. The network is backed up, fees are high, and transactions are slow to process. This gives the other smart-contract platforms a chance to pick up new projects and prove themselves.
From a scalability perspective. @dan made three blockchains that can outscale most of the rest. However, this is not the only variable when considering a "full glass". DPOS makes a lot of people worry that the platforms being created are too centralized and prone to corruption. Already EOS is under fire for freezing accounts without community consensus.
In truth, there are many variables to consider when picking a platform for a dapp. Focusing on scalablility alone seems incredibly short sighted to me. You have to consider decentralization, barrier to entry, overhead costs, simplicity, governance, community, inflation, distribution, and a myriad of other factors.
This perceived competition in the cryptosphere has been fabricated by past experience. Competitive corporate entities and governments are the only powerful forces the world has ever known. However, there is a new sheriff in town, and she goes by the name of blockchain. This open source revolution will eventually change the way we look at everything. From money and production to government and community.
There is absolutely no incentive to compete with Ethereum. A theory was going around that Block.One would flash crash Ethereum because they owned 10% of all the coins. Why would they do this? To make a point? Do we really expect Block.One to waste billions of dollars just to make a juvenile point?
When you consider that Ethereum is switching to proof of stake none of these "Ethereum Killers" have any reason to sell their coins. Why crash the value of Ethereum when you have massive stake in it? Clearly, these "Ethereum Killers" are simply going to stake their coins and boot up their own Ethereum nodes, further increasing the value of the platform. There is no reason for these projects to fight each other. They are all just trying to make a name for themselves and they are helping each other in that process. This is the alien nature of cooperative capitalism.