Ortiz' career had a confluence of things which are hard to imitate and stand outside of baseball to some degree:
1. He was a central principal in breaking the curse. And more than that - he had three walk off hits in that postseason ... how many people get that many chances, let alone cash them in
2. He never left - and was a heck of a comeback story, both from his time in Minnesota as well as his mid-career swoon in Boston which was overcome so completely that almost nobody remembers it.
3. He is the common thread through the entirety of the most productive era in modern Sox history
4. He enjoyed being famous. He was not an aw shucks sort - he loved the crowd back.
5. He was such a departure from the staid, racially problematic historical nature of the team. Not that he would not have been as beloved without it, but it infused a freshness and fun and energy to the proceedings which were historically very un-Red Sox with rare exceptions (like one with mutton chops and a very goofy looking wind up).
One of the heroes if the Cubs win it all will be a natural choice. The players cited are all good choices, but you have to have a banner - it would be hard to do it otherwise.
Andrew Miller could take on "folk hero" status, but that is a separate issue.