Only Rani had an "era" -- she was the top actress consistently for like 3 years in her prime. Preity was super popular, but she didn't enjoy consistent success or being at the top of her throne like Rani did.
The case with Ash is interesting. She doesn't really have an era or peak time. She peaked in 1999-2000 before coming again with Devdas in 2002. Then another slump in the next few years, but she received international acclaim and did some of her most critically acclaimed works during that period. After that, she had a pretty good comeback with Dhoom in 2006, and so on. So, while she was never consistent, she never went out of the picture like Preity completely disappeared. At least Rani is still doing decent works (Talaash, Bombay Talkies)
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