I think a Manager should have "range", Ellering was good but only had LOD and Snake for a short time.
Heenan - no brainer, had a stable, Hennig, Bundy, Studd, Flair and the list goes on
Albano - gotta love him, had a number of great wrestlers; Muraco, Samoans then later Bulldogs etc
Gary Hart - loved the obscurity, Muta, Missing link etc
Jimmy Hart - Personally I didn't like him but you do have to love his jackets, megaphone etc.