Ayumi Hamasaki - Japan
The best selling solo act ever in Japan, often called the empress of jpop, Ayu at her worst is still able get a level of attention most won't get at their best.
Namie Amuro - Japan
The current queen bee of the jpop market, Namie had an almost impossible 2nd peak on the very unforgiving japanese market, and even if she is almost on the 40's on a country most idols won't go past their 20's, she still is able to top the charts.
Madonna - USA
The best selling female singer ever in history, pretty much every female popstar who came after Madonna took something from her. Madonna is an integral part of the world's pop culture, and most likely nobody will ever get a career as glorious as hers.
Beyoncé - USA
If any popstar who rose to fame after the 90's is firmly positioned as a cultural icon, that's Beyoncé. She released her fair amount of songs, music and videos that determined what pop culture is nowadays and can be easily considered the lastest long therm world popstar the USA produced.
Ivete Sangalo - Brazil
Ivete's name is so big in Brazil that even people who dislike her body of work bow down to her career. She has the best selling live dvd ever released over here and is frequently selling out stadiums and arenas around the country more than 20 years after her career started.
Mylène Farmer - France
Mylène is around since the 80's and unlike most women on this list, her album sales still do give younger popstars a run for their money. She also sells out her tours in minutes. She also has the record for the most consecultive #1 singles in France.
Uhm Jung Hwa - South Korea
Also called "the sexy queen", Uhm Jung Hwa raise to fame in the 90's and is considered a major influence for the korean entertainers, having a successful (and much awarded) career in both singing and acting.
Kylie Minogue - Australia
Even if often called a pop princess, I do think the title don't do her justice both in age and success... Kylie may never really reached the same level of fame of Madonna, but she is around since the 80's as a major force in pop culture.
Thalia - Mexico
Thalia became a worldwide diva during her career as a telenovela actress, but her music career (that is far longer) can't be ignored either... She is spaming hits for almost 30 years and shows no intention of stopping.
Faye Wong - China
Faye may not really fit the usual pop queen image of having big broadway-like dance driven concerts, but with her own style of performance, she is a legend of her own.
Jolin Tsai - Taiwan
Even if often being seen as a lesser act by the western fandom of jpop and kpop, Jolin has been consistenly spaming hits year after year and keeping her name and image around as a pop icon on the chinese market.
Monica Naranjo - Spain
To be honest, her sound is not really my cup of tea, but she is huge on the spanish speaking world and has one of the 12 best selling albums in Spain. She as been around for years now and is a recordist World Music Awards nominee from her country.