With Botsis on this one. An "era" is a memorable, significant, or otherwise important period of time. I don't think Rihanus can say she's had a single era, only an legacy of flop albums. After all...
OK.
Here's the thing.
Her albums aren't "flops" by any reasonable definition of the term. None of them have hit number one on the charts, yes, but all but her very first have gone at least Platinum in the US. By your own definition, Janet's last two albums were terrible failures, and
Damita Jo barely limped across the Platinum line, if Wikipedia is to be believed. Talk That Talk will easily Plat, especially if WHYB keeps doing well.
She doesn't have a legacy of "flop albums". Her legacy is being a wildly successful pop star with a number of great hits despite having no redeemable qualities whatsoever.