I'm no expert by any means, I'm sure people can expand or add to the list.
Community: New coins are being created at an exponential rate. Unfortunately even if a new coin has all the bells and whistles of a prominent coin it may not be adopted purely because there isn't enough interest. Older coins have early adoption advantage.
Innovation: Does the coin offer something unique? e.g. algorithm, scarcity, mining style, transaction speed (efficiency).
Distribution: Are the majority of coins in the hands of a few, or is there a good spread? This says a lot about the fairness and stability of the coin long term as large holders can kill a coin when they dump millions onto the market (cashing out). Most new coins fail hard in this area as large miners dominate the market and then large holders use sneaky tactics as alluded to by Earthjade above.
Inflation: Due to the mining algorithms each coin has it's own inflation/deflation dynamic. Some coins will suffer from inflation as too many new coins are mined without the demand to purchase. Some coins will become so scarce that they will be tightly held and reduce liquidity and suffer deflation as demand slips away. E.g Bitcoin will eventually become deflationary (very long term) once mining is finished and coins are lost. ATM 25 new bitcoins are created every 10 minutes, and there is plenty of demand to soak them up.
Merchants: Can the coin be used to buy things? Ultimately to achieve anything like bitcoin status people will need to use their coins to buy things with. Bitcoin 2.0 platforms will expand on this with contracts, bonds, verification systems, P2P internet etc that will also attract investment (Ethereum, NXT etc. - I don't know much about this side of altcoins).
