I think you're right that OP meant the title to be "what should we invest in" so now I'm off topic...
I think the question "What will be the
best Altcoin" is very interesting though. I think it's determined by what makes a good currency, I think that's defined by basic utility (though not much, a currency is helped by, but not defined by its basic utility), scarcity, durability (keeps its value), and liquidity. Other things like fungibility, transportability are roughly identical between cryptocurrencies. Durability and liquidity are also basically impossible to predict, but they probably are influenced by the two other properties I mentioned, scarcity but moreso basic utility.
Looking at the best altcoin based on utility is a good way to measure it's success.
It's true that with cryptocurrencies we're not only looking at the value of a coin but also at the total banking system which comes with the coin. The total system must be well balanced and that balancing will make it succeed.
I think we are still in the very early adopter stage so it's hard to predict which will succeed.
As you stated most currencies are based on each other with minor and some fundamental changes.
I think the answer will become clear when some coins have been fully mined. What will happen will it become more durable? or will it die because mining is the most fun part?