How do you define a successful writer?

I just read an interesting blog about what criteria should be used to define a successful writer. Should it be down to the amount of sales? The number of good reviews? Whether you have won a prestigious literary prize? How much money the writer is earning? Or something else entirely – such as having their name and face recognised by the general public or having a film or TV series made for one of their books.
Also is a successful writer also a good writer?
I'll deal with the sales question first by posing another question:
To be successful does the writer have to sell thousands of copies of one title or can they be considered successful if they have dozens of books selling moderately well?
An author could have a runaway bestseller, sell half a million copies, and never write another book. Are these still successful writers?
I fall into the category of selling moderately well across dozens of titles with an occasional 'bestseller' in a few of the Amazon categories.I'm not sure if I would be considered successful or not using the sales criteria.
To move on to the second question – that of reviews.
My Regency books garner only a handful of reviews – mostly positive – but some stinkers too. However, my WW2 family sagas receive far more reviews but sell fewer copies.
I know a lot of store is put in having hundreds of five-star reviews on Amazon – they seem to be thought of as the holy grail – but when I check their sales ranking more often than not my books rank much higher than theirs. So which of us is the more successful?
Winning the Booker prize or some other such prestigious literary accolade could  be considered the pinnacle of success – but often these books fall into obscurity within a few months and sell only a few hundred copies. The writer has prestige but could they be considered successful?
Now I shall discuss  the question of money.
I make more than a living wage from my writing – 50% more than I got when I was working full-time as a top of the scale teacher. I consider that very successful but my aspirations and needs are possibly more moderate than others.
Do you have to do earn hundreds of thousands of pounds in royalties to be considered successful? In my opinion this decision is subjective. If I was just starting out, was half my age, I would probably think my writing royalties insufficient as my monetary needs would be much higher than they are now. Therefore, possibly success in terms of income is relative to each writer. I have a writer friend who is happy to earn a fraction of what I do. This pays for two luxury holidays year and so she considers herself to be successful as she's achieving what she wants.
I think that it would be hard to dispute the fact that being internationally recognised/having a film or TV series made from one of your books makes you successful in everybody's eyes. To have achieved that you must tick all the criteria boxes I mentioned above.
It would be wonderful to be able to produce one book a year like Lee Child or Bernard Cornwall and know you will sell millions of copies – but there are only a handful of writers that fall into this category.
I often see the names of indie writers quoted as being incredibly successful, having sold millions of copies of their books, and yet I've never heard of them. So maybe being internationally and universally recognised are not necessary criteria for being considered successful.
In conclusion let's consider if a commercially successful book is a good book. Fifty Shades of Grey illustrates this point perfectly. I found the book unreadable but millions of others didn't. It was definitely successful but I've not heard many, even the most devoted readers, say it was well written.
I would love to hear your views on this subject – maybe we can come up with a list of what makes a successful author.
Fenella J Miller