What about Google G Suite - a lot of people claim that it is comparable with Office 365?

It's certainly comparable, and does compete with O365. Legally, a monopoly doesn't mean it has no competitors, just that it dominates the market.

Some reports suggest that G Suite has more users than Office 365?

https://www.businessinsider.com/google-g-suite-gmail-2-billi...

NB I don't know how credible these reports are but I'm not sure that Office 365 "dominates the market" to the same extent as Windows used to.

Users aren’t customers. If you give something away for free, you will always have people clamoring for it rather than the paid product.

However people take what is free for granted and don’t consider it a part of the market. For instance, many hold that iOS is a monopoly despite being a minority of the market because you pay Apple for it, where as Android is just free and Google does not get your money for its use.

There has not been a free tier of GSuite since 2011. It is a commercial service that has a monthly cost per seat. There are 6 million users on GSuite for Business and 120 million on GSuite for Education. None of the grandfathered free Google Apps for Domains users are included in those numbers.

Google sheets, et al are free for personal use while Office 360 is a subscription as far as I know.

The numbers given in the article specifically are users not paying customers. As quoted:

> Google's G Suite boss Javier Soltero... did not say how many of those 2 billion users were paid

Additionally it indicates that Office may have more paying users:

> Google said roughly one year ago that 5 million businesses are now paying for G Suite, which pales in comparison to Microsoft Office 365's 200 million monthly active users of its version for businesses.

The conversation was about suites not individual applications. Even though you can use some of the separate GSuite applications for personal use, you cannot get GSuite for free. There is no free tier.

Likewise, there is no free tier of Office/Microsoft 365, but there are free services that are considered part of this suite. How many of the 200 million monthly active users are customers? How many users were paid? If a person uses the free tier of OneDrive, OneNote, or Skype they are not considered a customer even though they are an active user.

When you compare, you do like for like. The comparison is GSuite to Office 365, and many independent studies have said Google has a larger market share.

Something about G-Suite feels like an also-ran. None of the offerings are quite as good as Microsoft's with the exception of Gmail.

That Office is for many people an objectively better and more powerful tool doesn't inform whether it holds monopoly status.