People are also naming those who are considered sexy or hot or 'unconventionally good looking'.
Plus you used the word 'heart throb' in title which has led people to name Vicky, Ranbir, Ranveer and even Ajay.
Considering RS and RK have been 'heartthrobs'.
Anyway, coming to your OP, I would like to respond that earlier people had different standards of beauty. They liked voluptuous women, full figure, big eyes, curvy women, well aligned teeth. Hema Malini is closest to what Indians depict in idols of goddesses or paintings or calendar art. She also dances well and that is a bonus. Her large eyes and long eye lashes, doe eyed beauty, chubby cheeks, curvy body were considered her asset.
She was compared to goddesses and apsaras back then.
And she maintained self rather well with those surgeries or botox and yoga etc which is why she was called timeless beauty and even John Abraham said he had crush on Hema. Her looking younger and well maintained for her age has only added to her timeless beauty myth.
She also knows her appeal which is why she has done a lot of period films, tv shows and costume dramas or played goddess or performs in mould of devi or apsara in classical dance performances also.
People forgive her for her bad voice. She was wildly popular in 70s and giving even heroes a run for their money.
Indians like full figure. Most Indian women are not slim nor tall. There is a reason why even Sonakshi was a hit in massy films despite her weight issues. And some call Deepika 'flat' or say aaj kal ki ladkiyo mein woh baat nahi hai.
Partly Madhuri's appeal also lay in her full figure and heaving her breasts and buttocks in cameras and dancing to suggestive songs while pretending to play sanskari bahu. She appealed to Indian ideal of Sati Savitri outside and hot in front of males or in dreams of males. Cleverly makers would cast her in seemingly pious role but make her do cheap songs in name of a fantasy or 'majboori' of woman forced to dance like Tezaab, Yaarana or Devdas or as some trap for criminals like Khalnayak. She, Rekha, Dimple and Sridevi are also first mainstream heroines to do elaborate love making scenes, kissing scenes, with all those noises, expressions and topless or backless stuff or giving impression of being wrapped in bedsheet or towel. The so called love for looks comes from these antics also.
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