Burt Ward's Dick Grayson/Robin, because he was a teenager, and because of incredibly bulgeworthy costume. We all but ignored Adam West's Bruce Wayne/Batman.
During the decades since Batman ended, Adam West has had a substantial career playing quirky, out-of-touch parodies of himself on everything from The Adventures of Pete and Pete to Family Guy (where he plays "himself" as the Mayor of Quahog). Delightfully quirky, but not much in the muscle department.
Born in 1928 in Walla Walla, Washington, West started his career in comedy, as the host of a live children's show in Hawaii and someone named "Ham Ector" on the Philco Playhouse, but in 1959 he moved to Hollywood to join the beefcake craze -- dozens of hunky actors, many discovered by Henry Willson, were tearing up the screens with shirtless and swimsuit shots.
He became very busy immediately, with 10 roles in 1959 alone, notably in The Young Philadelphians, as a man who cannot consummate his marriage for unspecified reasons (i.e., he's gay). He rushes off and dies in an auto accident. His wife has sex with someone else, and his "son" grows up to be Paul Newman.
Robinson Crusoe on Mars, and the hunk-meets-feral-girl Mara of the Wilderness.
Like many men of his generation, West was somewhat homophobic; in the 1980s, he was flown to London to appear at an event, but when he discovered that it was gay-themed, he refused to appear.
More recently he commented on the gay undertones of Batman: "gay, straight, whatever. Add them to the ratings. If gays like the show, wonderful!"
He died on June 9th, 2017.
See also: Lane's Hookup with Batman, RObin Joker.