Genesis mining and Hashnet (Bitmain) are real miners. (Proof: Their signed mining address) and I can vouch for them.
Minergate too holds a large pool and might have some good mining hardware and is my second choice.
ViaBTC, one of the largest exchange and pool are also offering cloud mining service.
Hashnest is a legitimate mining operation, but that can't be said about genesis mining. From there I am very interested in the signed message from one of GM's mining addresses.
GM has been refusing to sign or even show their Bitcoin mining address, and that's going on for years now. It's nothing more than a scheme that eventually will vanish with people's money ~ that's a guarantee.
Also, just because Hashnest is a legitimate mining operation, this still doesn't mean you'll get to ROI at whatever time frame ~ cloud mining in general is one big joke.