If I were to tell you what the most profitable coin was, by the time you started to mine it, it would most likely not be profitable.
Mining any coin has a number of things that affect it's profitability:
1) Difficulty to find
2) Amount of hashing power you can commit
3) Current/Future value
4) Ease of use and/or liquidity
5) Complexities in the ecosystem of the target alt coin
6) Complexities between all alt coins
7) Complexities in the anchor currency (The one you convert to USD/EUR or what ever), for me this has been BTC.
The current/future value can be artificially pumped up when people start the comments about the next big thing. For instance Dogecoin has seen some increase in value, just by being mentioned. What does it really have to offer?
As long as there is someone willing to buy them you can sell them. Since mining is a longer term venture, you need to consider the complete eco system and landscape.
I just made some money on
www.vircurex.com. Here's what I did.
I had NMC that I sold for DOGECoin which I then sold for LTC which I then sold for BTC. I made 25% more than if I just sold NMC -> BTC.
To do this right you need to be able to model the differences between the currencies, place limit orders and be patient.
