It's worth asking why. Some part of this lack of recognition had to do with the fact that Dharmendra acted in heroine-oriented films in the early part of his career. He was paired with major actresses like Nutan, Mala Sinha, Meena Kumari and Suchitra Sen who got the credit for the films they made together; Bandini, Anpadh, Phool aur Patthar and Mamta are good examples. He played the romantic foil and because he was so comfortable in his skin, so effortlessly the good-looking, honourable male lead, his audiences ended up thinking that his roles didn't require real performances. Then, in the early '70s, some of his signature performances came in multi-star films. In Chupke Chupke, while he carried the film, he shared screen time with Amitabh, Sharmila, Jaya Bhaduri and Om Prakash. Similarly his great comic turn in Sholay had to share attention with Sanjeev Kumar's eye-rolling histrionics, Bachchan's tragic end and, of course, with Amjad Khan's extraordinary debut as Gabbar Singh.
It's possible to find semi-plausible reasons, then, for Dharmendra being overlooked in the acting stakes, but these aren't good reasons. When you consider that Rajesh Khanna was celebrated for his performances in Anand and Namak Haraam, performances that are hard to watch today without giggling or cringing, when you think of the millions of movie-goers and critics who thought Sanjeev Kumar's kit bag of theatrical mannerisms made him Bombay cinema's greatest actor, when you recollect the endless variations on vigilantism that installed Bachchan in our memories as an acting Atlas, it's hard to believe that Dharmendra got so little credit for so much good work. Even Sunil Dutt, who was no one's idea of a great actor, got two Filmfare Best Actor awards in the early '60s.