It's a common question made by who is new in this world, and the answer is always the same, it's a scam.
If you see about the genesis mining and hashflare it looks like the legit cloudmining site but it will never give back your ROI and it's also including on the scam site. 
They have a lot to lose when it comes to tarnishing their company name with not paying or doing any sort of funny business with customer accounts.
Maybe in the eyes of many users Genesis Mining and Hashflare appear to be trustable, but for example I have a lot more trust to HashNest!
The most important difference is that when you sign a contract with GM or Hashflare, you can not withdraw from it. HashNest has its own market where you can always sell your power, withdraw funds and go.