Blocknet is by far one of the most profitable ones you can find long term. They where the first project to launch a true DEX. Established in 2014 - Pretty low entry point right now, (5000 coins required).
You'll be able to profit from:
Masternode rewards
DEX trading fees
Decentralized Oracle fees (From their XRouter tech)
It's by far the most reliable income you can find, besides DASH, and perhaps Bitshares, but they are crazy expensive.
The yearly ROI is pretty amazing as well.
How much is yearly ROI ?