Oh, this is my jam. Don't think of it as a ladder, think of it as a spectrum. On one end, you have the gentle, profound depth of stories like 'Surya Vamsam'—the romance is woven into family legacy and quiet understanding.
Then you slide over to the fiery, obsessive intensity of 'Nenjil Oru Mul' where the emotions are so loud they practically leap off the page. The depth there comes from exploring jealousy and possession, which isn't everyone's cup of tea but is undeniably potent.
Most of her classics sit somewhere in the middle, balancing societal conflict with personal yearning. The 'depth' often comes from the heroine's internal journey towards self-worth within the relationship. So a ranking is pointless; it's about what flavor of romance you're craving on a given day.