Relatively speaking, no blockchain in existence today is very good. We are seeing this technological revolution unfold at exponential speeds. It stands to reason that the best coins haven't even been dreamed up yet. I believe we will begin to see them once the tipping point has been reached.
The tipping point is when blockchain tech can no longer be denied and becomes mainstream. The establishment will do what they've always done; buy/snuff out the competition. They'll try to buy out all the good coins and bend them to their will. They'll make their own inferior coins and claim they're the best. I won't even be surprised if spy agencies like the NSA go around stealing as much as they can behind closed doors with the absolutely ridiculous access they have.
This will be the time for blockchain developers to get very creative. They'll have to create chains that are fully decentralized and very resistant to corruption. Luckily we are already half way there. Many chains are somewhat decentralized and somewhat resistant to corruption. As long as people HODL they can't really be bought out either. Still, there is massive room for improvement.
@dan Larimer had the right idea with EOS. The year long ICO phase promotes decentralization in a big way. EOS doesn't do anything right now so it sits at #6 on the market cap based on hopes and dreams alone at this point. Pretty impressive.
However, just like @dan abandoned Bitshares and Steem he'll come to realize (if he hasn't already) that EOS also has fundamental flaws. It's all part of his journey. He's creating the technology that he needs today so that he can make an ultimate coin in the future.
One of the big problems with the cryptocurrency space is that it's very hard to identify individuals. EOS and Manna are two front-runners attempting to solve this problem. Proof-of-existence. One account for one person. This is a very big deal for establishing an individual's reputation and identifying bots. Universal basic income projects like Manna will fall apart if one person is able to sign up for multiple accounts.
Being able to identify unique individuals online (while also not compromising privacy) will pave the way for ultimate coins. When someone tries to exploit the system, their transgression will be logged and they won't be able to just make another anonymous account with a clean slate. The dynamic reputation systems of ultimate coins will be complex and difficult to bypass. I fully expect at least one ultimate blockchain to not even have a currency associated with it. Your reputation will be all that matters.
Ultimate coins hinge on the ability to identify unique individuals. Just like proof-of-work is becoming outdated so will proof-of-stake. Proof-of-existence and proof-of-reputation are the way of the future. In the end, even ICOs will become outdated. They do not promote decentralization of wealth.
Vision
My vision for an ultimate coin starts with universal basic income. Proof-of-existence has been worked out by then and every unique individual will get an equal amount of coins per week. This dynamic promotes perfect decentralization. Everyone starts off on an even playing field. Once there are a certain number of coins in the ecosystem a transition is executed. Much like Ethereum switching from proof-of-work to proof-of-stake with the Casper protocol, this ultimate coin will switch from proof-of-existence (UBI) to proof-of-reputation. The inflation mechanic changes from UBI to rewarding users that interact with the platform in the most positive way.
A coin like this needs no ICO. It doesn't rely on fiat at all. It stands alone. It's value is massive because a billion+ people are using it due to the fact that coins were simply given away at the beginning. It retains it's value through complex reputation systems and accurate ways of judging contribution and trustworthiness. You may call me a dreamer, but I'm not the only one.