A lot of great names, on balance, so far. Here's another, Henry Hank of Detroit, He never dodged anyone. In the late 50's and into the 60', as a rated middleweight, he took on many top lightheavys and won his fair share of them. Hard puncher with a pleasing style.
No mention Bad Bennie? Eugene Hart? J.Roldan? Hamsho? Obeijimas? The last 3 could've won at least a version of a Middleweight Title in other eras. Unfortunately They came along when "Marvelous " was at his most destructive best.
Flash, you have to read the posts. Most of those you mentioned have been brought up a number of times already.
Mike Gibbons Charley Burley Holman Williams Eddie Booker Dave Shade Jack Chase Jeff Smith Leo Houck Jack Dillon Billy Conn (Conn and Dillon both GREAT middleweight contenders before winning LHW crown)