Well, is there?
Here's a shortlist I came up with:
1970s & '80s -
M*A*S*H -- Radar O'Reilley (Gary Burghoff). A sweet kid who is at times the conscience of the unit. Without him to organize things, the camp would collapse under the weight of all the wackiness, laziness, ineptitude, and a gazillion military regulations that make little or no sense.
MARY TYLER MOORE -- Georgette Baxter (Georgia Engel). Takes "naive" to new levels. Not exactly brilliant, but a total sweetheart. Hard to believe she married Ted Baxter (Ted Knight), that egocentric blowhard, but she must see something in him that is absolutely invisible to other human beings (kinda like sounds that only dogs can hear).
ALL IN THE FAMILY -- Edith Bunker (Jean Stapleton). Kind & loving & generous, she thinks the best of virtually everyone. Another wife of an obnoxious character -- in this case, Archie Bunker (Carroll O'Connor) -- who gives that character more depth simply because you know there must be something more to him, below the surface, something worthwhile that the rest of us can't see.
CHEERS -- Woody Boyd (Woody Harrelson). Dopey & small-town-boy sweet.
NORTHERN EXPOSURE -- Ed Chigliak (Darren E. Burrows). Innocent & decidedly odd. One of the most unique TV characters EVER.
BONES -- Dr. Lance Sweets (John Francis Daly). Not innocent, certainly, but sweet, touching, emotionally needy.
ROSANNE -- David Healy (Johnny Galecki). Nice, sweet, a good boy. We'll overlook the fact that he eventually knocked up Darlene (Sara Gilbert).
NCIS - Tim McGee (Sean Murray). Naive, a true boy scout.
LOST - Hugo "Hurley" Reyes (Jorge Garcia). Kind, sweet, wants to help ... well, everyone. Wouldn't we all like to hang around with him, playing his version of golf and munching on Dharma candy bars? ;-}
Who would you add to the list?