Dr. Rajkumar was also one of the most versatile actors in Indian cinema. His character depictions ranged from comedy to action, from lover to double/triple roles, from mythological characters to portrayal of modern day social causes. He acted with the most popular heroines in southern Indian cinema, such as Kannada's Pandaribai, Leelavathi, Jayanti, Bharati,Arathi,Jayaprada, Madhavi, Geetha, Sarita and others from neighbouring states. He acted with many directors of the south Indian cinema from B.R. Pantulu, Puttanna kanagal to Shankar Nag and Nagabharana. With the exception of one Telugu movie called "Kalahasti Mahathyam" he acted only in Kannada movies. Actors who have acted with him considered it an achievement of their lifetime. Prithviraj Kapoor acted in the movie Saakshatkara in the role of Dr. Rajkumar's father.

In his lifetime, Dr. Rajkumar acted in 206 Kannada movies, excluding guest appearances. He owned a film production company called Vajreshwari Production, which produced films under the banner of Dakshayani Combines. Bhagyada Bagilu was his 100th movie and Devatha Manushya was his 200th movie.

Two of his most famous performances were in his own productions:Kaviratna Kalidasa and Shankar-Guru. He produced movies based on famous Kannada novels. He was ably supported by his friend and script writerChi. Udayashankar. He signed films only after consultation with his brother, S.P. Varadaraju. He chose stories that usually had a social message for the audience. He also made many movies against social evils. One such movie is Shabdavedi which is against the evil of drugs.

He never smoked a cigar/cigarette or acted as an alcoholic in any of his movies (excepting a few in the early days of his career). In real life too, he was a non-smoker and non-alcoholic and maintained a very high standard of living, performing daily Yogasana and following a strict diet.

Though he had numerous chances to try his hand at Indian politics owing to his mass following, he shied away from active politics focusing his energy toward art and cinema. His last movie was Shabdavedhi (2000), in which Jayaprada played the female lead.

His most memorable films include Bedara Kannapa, Bangarada Manushya, Kastoori Nivasa, Sri Krishnadevaraya, Kula Gowrava, Gandhada Gudi, Sampathige Sawal, Shankar-Guru, Babruvahana, Bhakta Prahalada, Halu Jenu, Bhagyada Lakshmi Baramma, Jeevana Chaitra, Akasmika, Premada Kanike, Vasantha Geetha, Apoorva Sangama, Daari Tappida Maga, and many others.