I think the discussion on the best investments, depends on our definition of what "best" is.

Investment returns will generally be correlated with risk, so:
(1) High risk, high return short-term trading strategy ("buy low, sell high"): But can you read the market well enough to generate the best trading strategy? For every buyer of a coin, there is a seller, so who is doing it wrong?
(2) Moderate risk, moderate return portfolio investment strategy e.g. Keza (http://www.getkeza.com) as an investment platform.  But you need to invest time in selecting the right investment portfolios based on the composition, underlying beta and future outlook.
(3) Low risk, low return secured lending strategy (collateralised lending).  But need to vet borrowers based on past track record too.

I would avoid HYIP, Ponzi schemes, and grandiose promises.

http://themerkle.com/bitcoin-investment-startup-keza-unveils-ios-beta-app/
https://www.producthunt.com/tech/keza
http://getkeza.com/ (It's free to apply for a Keza account)