I didn't see Don Shula's name mentioned at all, unless I missed it. The stadium at John Carroll is named for him. He played for the Blue Streaks in the early 50s.

Pete Metzelaars, who I believe still holds the NFL record for most games played by a tight end, was a basketball All-American and football star at Wabash in the early '80s.

Billy "White Shoes" Johnson was a football standout at Widener in the early '70s before going on to become a legendary kick returner for the Houston Oilers.

Prominent names from the MIAA:
John Porter, Albion, 1952 men's basketball Most Valuable Player - went on to become president of Eastern Michigan University and superintendent of Detroit Public Schools.
Fritz Shurmur, Albion, 1953 football Most Valuable Player - went on to a long career as an NFL assistant coach, most notably as defensive coordinator for the Green Bay Packers and several other teams.
Cedric Dempsey, Albion, 1954 men's basketball Most Valuable Player, also played football and baseball - became athletic director at several major institutions, including University of Arizona, and later President of the NCAA (1993-2002).
Bob Devaney, Alma, 1939 graduate, was an All-MIAA end in football who went on to lead Nebraska to two national championships in the early 1970s.
Jim Northrup, Alma, 1959 football Most Valuable Player - went on to play 12 seasons of major league baseball, mostly with the Detroit Tigers. It was Northrup's two-run triple off Bob Gibson in Game 7 of the '68 World Series that propelled the Tigers to the series-clinching win.
Jim Kaat, Hope, All-MIAA selection in baseball in 1957 - went on to pitch in the majors for 24 seasons, winning 283 games and a record 16 Gold Gloves for his defense.
George Pyne, Olivet, three-time All-MIAA lineman in football in early 1960s - played for the AFL's Boston Patriots, part of the only family to have three generations play professional football.

More to come...