Many viewers have panned this series. It was hockey and implausible at times. However, I recently watched the series again on the Westerns Channel and offer these observations:
When "Wanted" first came out in 1958, network TV was flooded with formulaic Warner Brothers westerns. With few exceptions they were all mostly repetitive and forgettable. My picks for exceptions are, obviously, Gunsmoke, which stood above the others, Have Gun Will Travel, Maverick and Josh Randall's Wanted Dead or Alive.
For the mid 1950s McQueen's character was ground breaking. He was the first anti-hero in a horse opera. Even when grouped with the line up of special gimmicks westerns (the rapid fire Winchester of The Rifleman; the weird Colt of The Rebel; Wyatt Earp's Buntline Special), Randall and his hog leg stood out. Never mind that he didn't reload and the mechanics of the weapon were implausible, the series worked. It was unique. McQueen was unique.
I was 11 years old when the series started and it hooked me. Sure, it is difficult to watch it today without a laugh or question about its relation to reality. But back then it was cool and so was McQueen. And as someone else commented, only McQueen could have played the character of Josh Randall. For that matter, look at all his motion pictures. I don't believe any other actor could have made those films what they were.
Even 25 years after his death, McQueen is as popular as he ever was. As far as I can see, only John Wayne still has that kind of appeal.