Hashflare has good roi but I don't know much about them, some people says bad and some good....
Genesis was proven as a scam.
And yes, there was a thread about how bad ROI does minergate has: https://bitcointalksearch.org/topic/minergate-cloud-mining-test-real-numbers-its-scam-2671027
Worst part about mining over minergate:
If you ever mine an alt there, you'll personally notice that while they claim that they charge less fees compared to other pools, they literally lower the amount of coins that we are expected to get, and we get few % less coins. I've stopped using them for any purposes whether it be mining or purchasing their cloud plans.