Magnum PI. It is my favorite show. I also really miss "Frasier", "Seinfeld", "Friends", "Good Times", "Chico and the Man", "What's Happening!!", "Midnight Special", "The Good Guys", and "Brisco County Junior" (though I thought it was called "Crisco County Junior" for the longest time. I don't hear things correctly sometimes).
I also miss some of the shoes from the eighties. TV today is over run with reality programming. As for a specific show, I'm really embarrassed to admit I miss "Love Boat." It was the corniest show ever.
I don't miss any of the old shows. Many of them were taken to the point of being redundant. Don't get me wrong, they are the only ones I like. What I miss is the quality of the old shows. I could watch a different episode of Bonanza every day for a couple years before I got bored.