Basically, unlimited isn't unlimited! (skip to the line and big words below if you want to skip out a small rant/why/how unlimited providers work!)
Trust me, Some web hosts offer unlimited everything for less than $7 a month... if this was possible, Microsoft and all the other big places would use these and save millions! The fact is... it is a lie!
Most people who have a website online will get less than 10 visitors a day and take up around 50Mb of web space. They cost a few pence (if that) for a host to maintain one of these accounts.
Then, there are a few sites who may have a hundred or so visitors a day and use up ~5GBs of hard drive space... On these sort of accounts, the host may make a small profit or brake even.
Next are the Bigger sites such as game communities, popular forums etc. They may have thousands of visitors a day and take up 10GB of space. The webhosts usually make a small loss on these accounts, but they use monitoring and study logs to place these on servers where the resource usage is low - offset by the profit of lower sites
Lastly are the huge sites... When a "Bigger" site becomes to big, they will simply recommend you upgrade your account or terminate it.
Your website may be on a machine with hundreds or thousands of other sites and simply it is "hosting" but there are no guarantees.
Now about Google and "Cloud" providers
Simply, you get what you pay for. These services do not oversell on the hopes that some people do not use their allocation, they simply will charge you for what you use and you should never be terminated for using to much... You simply pay more and get more resources.
Cloud services are expensive compared to a normal host. What I recommend you or anyone does is simply use a normal shared host if you have no special / out of the ordinary requests (if you do, either speak to a host to see if they can accommodate or go virtual private server), then if you don't mind a bit of hassle go either dedicated or colocation - if you do not want the hassle and worry about clustering, failover and all the rest - go cloud.