Sherlock’s older brother, Mycroft appears in a variety of forms, but he’s usually a figure of authority, and always something of a mirror for Sherlock, for better or worse.
Corbin Bernsen (Psych) — While not strictly a brother, Henry Spencer still functions like the Mycroft of the other adaptations. He’s an older family member, an investigative equal (or at least nearly), with a troubled relationship to the hero. Henry’s appearances are usually to impart some sort of (unwanted) wisdom, or to provide help with a case, or simply to generate comic relief. A solid character. I like him a lot.
Tony Goldwyn (Law & Order: CI) — Frank Goren, far from being an authority figure or a source of help, is a cautionary tale for his brother. Wracked by mental illness, and often-as-not living homeless, Frank reminds us that Bob Goren is always a few steps away from the sanitarium. His performance is creepy and haunting.
John Turturro (Monk) — Ambrose Monk, like Frank Goren, is a way of showing how much worse life could be for Adrian. This older brother is smarter, but he’s also debilitated by agoraphobia and a grab bag of other mental instabilities. Turturro creates a performance that is touching and hilarious. This is my favorite of the Holmes Lite Mycrofts.
Stephen Fry (Guy Ritchie film series) — This Mycroft hews closest to the original. Smarter than his younger brother, he functions as a fixer for the British government. Fry’s Mycroft is eccentric and unflappable, but not particularly interesting.
Mark Gatiss (Sherlock) — Another close adaptation, this quipping, manipulative Mycroft works for the government and doles out tidbits of information to his brother only if it advances his agenda. His obvious real concern for Sherlock mitigates his singlemindedness. Gatiss’s performance is arch, but still lived in. This is very nearly my favorite Holmes Proper Mycroft, but I have to give it to…
Rhys Ifans (Elementary) — This Mycroft is a charming restauranteur, a bit of a bully to his younger brother, but the rough treatment hides a caring heart. Throw in a difficult illness and a bit of flirting with Watson, and you’ve got the makings of a really interesting character.
Overall Winner: Rhys Ifans