As a counter-example, “MAS*H” worked fine with Hawkeye as an interesting protagonist, as opposed to just a straight man, someone who could (and, once, did) carry an entire episode on his own as the main protagonist of the whole series. Of course, Hawk could also (and, often, did) act like a straight man to the really nutty people and events around him.
I disagree that “Star Trek” was all about Kirk and Spock: It was all about the power trio of Kirk, Spock, and Bones, with each of them forming one side of the discussion about what the plan would be: Spock was the voice of reason, Bones was the emotion and conscience, and Kirk had to mediate the extremes and decide on a specific course. Really, it’s proof that Freudian psychology works better as drama than treatment.
Oh, and Kirk wasn’t a flat character. He was a classic trickster hero, relying more on subterfuge and negotiation but being capable of fighting.
Well, sure. At that, MONK was built around Tony Shalhoub carrying episodes as the oddball playing off his level-headed assistant and the hardworking cop who genuinely respects his abilities – and, granted, Randy Disher is pretty much just there to serve as comic relief, but he’s still less eccentric than Adrian Monk.
When I saw the title of this thread, Johnny Depp’s Tonto was the first example I thought of. I couldn’t even remember (until seeing the name in your post) who played the Lone Ranger, or anything he said or did in the movie.
Likewise, Disney’s Aladdin seems to be mostly about Robin Williams’s genie, and secondarily about Jafar and the Gilbert Gottfried parrot character. Wait a minute, was Aladdin even in that movie?
Remember Caddyshack? That was all about Rodney Dangerfield and Ted Knight, right? I think there was a caddy character in there too, but I can’t remember anything about him.
I am kind of torn on Deckard. Ford did a pretty awesome job of making him seem Spade-like (Hammetesque?), but a fair amount of humanity leaked out around around the edges. Really, again, I think the city was a more significant character than any of the people.