Depends what age group you asked. Nova and Triple J would be more recognized for many. I think actually Nova has a higher profile and recognition than Triple M these days, at least in metro areas.
To be technical it’s not 2MMM people are recognizing either. Remembering 4MMM went to air about the same time and was initially known as that before (and after) FM104. The other stations in the network were re-brands of course.