Three for me. Once on PC (when it was the first action RPG I’d ever played), once on Xbox (for which I even bought all the DLC, even the cosmetic stuff), and finally the Legendary edition on PS4 (which gave me the extra FPS to be able to complete it on Insanity)
I recently bought the Legendary edition, although I already own the first three games, so technically I bought it twice. I mainly did it for the visual upgrades for ME1 and ME2.