Here are some recommended novels with a male protagonist who is an older gentleman and deeply in love with the female lead:
1. "帝寵" by 卯蓮: This heartwarming novel features a significant age difference between the male and female leads. The male lead, an emperor, has been by the female lead's side since childhood, providing her with love, friendship, and protection. The story explores their evolving relationship and the challenges they face due to their age difference.
2. "掌心寵" by 泊煙: This novel portrays a tender and subtle romance between the male and female leads. The male lead's pursuit of the female lead is filled with love and affection.
3. "西月已歸" by 黃魚聽雷: In this novel, the male lead is a caring and gentle older gentleman who falls in love with a young and lively girl. Their relationship is hindered by their age difference and social status, but their love for each other gradually grows.
Please note that these recommendations are based on the provided search results and may not encompass all novels fitting the criteria.