So the coins that are likely to succeed are those with:
1. Trusty developers. This is the most important one. Without trust, the coin is doomed. (check out this thread for POD ratings:
https://bitcointalksearch.org/topic/poll-what-anonymous-coin-will-succed-568166)
2. Features. Does the coin offer something else than bitcoin? Does it have any unique features that makes it stand out? Does it have a solid roadmap for upcoming releases? Does the devs live up to their promises?
2. An active community. If noone has faith in the coin or is interested in it besides making quick money, it will never grow.
3. Marketing. To reach a bigger audience it needs marketing. This can be both from the devs or the community.
I chose my coin investments by those criterias. Trying to "game" the market and make a quick buck is just gambling, and it is mostely rigged by pump and dump groups.
I chose XST as my primary coin to invest in, but you may have your reasons and biases for choosing your investments. What is clear is that if bitcoin fails, for security or other reasons, altcoins will quickly become very very popular and only the most promising ones will be adopted.
You should look beyond simply a developer you can trust. There is a difference between a developer with an IQ of 110 compared to 140. There is also a difference in between a skilled developer with decades of programming experience compared to someone with just a college degree in computer science. Furthermore, I look for developers that are heavily invested in their projects as they are more likely to be dedicated to them, and ones that do not overextend themselves across multiple projects a la jl7777.
Your points as to features are good, I would also add ease of use and improved features upon Bitcoin.. not necessarily new features although that is good too if they are innovative enough to stand out as you said.
I agree communities and marketing are very important, but perhaps less important than the above two factors (in my opinion), as if your ideas, innovation, and implementation are solid then the community and thus marketing is sure to follow. I think most marketing is formed by communities and the best form of advertising is by word of mouth, so communities and marketing are mutually inclusive and after effects of solid innovation and implementation.
Also a few more things I think are important:
Making sure that it has a fair and decently distributed release. Innovation can overcome this (ripple), but it will be a permanent black eye that people will always use against the crypto and it takes revolutionary innovation to overcome.
Possibility of achieving a network effect. If another larger crypto is already doing on what you plan to do, it will be tough to overcome their network effect. Also, finding cryptos that are doing something really different are more likely to succeed off of achieving their own network effect.
Does the crypto solve a problem in society or a problem in other cryptocurrencies that could cause it to have value in the future and overcome a larger cryptocurrency's network effect? I don't think minor changes/improvements are enough to overcome network effects.
Maybe these things were covered in your more generalized statements, but cryptocurrency analysis can never really be extensive enough. I am sure I am forgetting a few things.