A good altcoin needs:
Real world features that meet real world needs, that don't exist on any other network, or are implemented in a better way.
These features should be
Network features - what can you do with the system, and how do you do it
Community features - how to connect users of the system
Governance features - how to manage the growth of the system
Gateway features - how to connect this system with other systems
Blockchains are a certain type of Database, your wallet is just a way of interfacing and altering the database. So the question is, what types of efficiencies can be drawn out of this new type of database/network? There is already a growing array of uses. Currency (bitcoin, litecoin, dash) blockchains are over saturated. very rarely does a new interesting one come out. To grow an interesting currency chain, it really needs to focus on usability and user features. Smartcontract chains are also pretty over saturated (ETHEREUM, NEM, NEO) but are much less developed, as they are a much more complicated system (which is why there is a lot of FUD around ethereum). There are APP coins like SIA which is about decentralized distributed cloud storage.
There are many very interesting altcoins, at this point all advantages with bitcoin have to do with the network effect (biggest userbase, most well known, most applications built around it) otherwise it is the most outdated blockchain of any value. It is a very slow network, both in operation, and in how it upgrades (upgrading slowly is part of it's security however).
I think you have missed the time transactions take to proceed (they should be instant) and safety of the code (no problems of the kind which we see ethereum has).
And yet I think that even a coin having everything quite perfect may stay being unnoticed and worth nothing. And it may stay this way forever. A coin has to be advertised somehow, so that someone decides to build, say, a casino operating only with it. Then people might realize it is indeed better than anything they've seen and maybe the coin will have a chance to be noticed. I think the winning coins are not the best ones.
