I think the distinction, within the example set you give, could also be:
1st gen: Bitcoin or derived by forking Bitcoin with a new blockchain and modifications
2nd gen: Bootstraps from existing Bitcoin blockchain, or uses brand-new codebase
One of the major changes of this generation is the introduction of philosophies about money beyond the "gold-like" model that drove Bitcoin. In particular I see two unique features:
1. Enabling financial derivatives to live on-protocol
2. Omitting proof of work in favor of new methods of currency release
I find part 1 to be less worthy of interest. Derivatives markets have a place in creating liquidity, but aren't fundamental to finance, and I'm wary of some of these implementations that try to hew too closely to a model like forex or options - complex trading models ultimately favor financial specialists. Nxt has the colored coin option planned, of course, which may prove to be good enough for individuals who want to make simple investments.
Part 2 interests me profoundly. At heart I hold the opinion that an equitable redistribution of wealth is desirable; not to the point of rendering currency meaningless, but as a long-term force to dampen inequality and keep the global economy from stagnating. As such, I expect a gradual trend towards equitable-redistribution strategies in new cryptocurrencies, because a currency that demonstrably produces more stable economic outcomes is winning on the most important intrinsic of any "medium of exchange." I don't think any of the 1st gen coins are anywhere close to this, since the mining process is unequal-redistributive, and thus destabilizing. Nxt remains deflationary in basis, but is also a strong step towards stability, since wealth in the system remains in proportion over time until actors choose to transact - with a very slight bias towards appreciation due to lost coins. Nxt relies on the social expectation that its early adopters will be rational enough to spread around proportionate wealth in order to gain real wealth. eMunie is also taking a step towards stability guarantees, since it designed in a feedback loop for a self-correcting level of inflation.