There used to be a time when Henry Blofeld and Tony Greig were primarily the only ones who'd get behind the microphone even during matches where teams of their patronage weren't involved. While Henry's Etonian sentences constructed in a distinct voice might have been lost on the more recent cricket followers, Tony's more "accessible" din can still be heard coming out of teletubes around the cricket world.
But there was a period there - through the 90s and even into the early part of this millenium - when commentary teams were almost reduced to a pseduo matchup of the series, only off-screen.
Ravi Shastri would be teamed up with (or against as you might want to see it) David Gower. Rameez Raja and Michael Holding. Ian Smith and Ian Chappell.
Is there a new trend developing more recently? Sanjay Manjrekar often goes to Sri Lanka whether or not India's playing there. Mark Nicholas, Mike Haysman, David "Bumble" Lloyd, Robin Jackman, Ravi Shastri, Rameez Raja, Ian Chappell and the likes have all been heard in series where their teams haven't played.
The latest addition seems to be the Rolls Royce himself, Michael Holding, who can be heard in the current Ashes.
On the other end of the spectrum, we also have specialists like Tony Cozier who exclusively follows West Indies ... well, actually his stature is such that now all of West Indies follow him .. .ala Richie Benaud for Australia. And speaking of Australia, Simon O'Donnell, Bill Lawry and Ian Healey seem.to be stuck to Australia's own Channel 9.
Of course, Tony Greig can still be heard everywhere.