The point wasn't that Greenidge's side had the best attack, like Australia's. The point was a lot of the great bowlers during Greenidge's era were in his own side. Hadlee is an all-time great, but he is surrounded with the Chatfields. Imran is great, but he is surrounded by the Sarfrazs (until the late 80s where Wasim and Waqar show). And was generally poor whenever he faced Lillee. IIRC he was pretty good when Botham was at his peak though - also against Willis. That's about it for great attacks of his time, the majority of good pacers were in his own side: Roberts, Marshall, Holding, Garner, Ambrose, Walsh, Croft, Bishop, etc I wouldn't call these great attacks anymore than I would the Sri Lanka of the late 90s.
And amongst contemporaries: Hayden is top, Greenidge probably 3rd.
P.S. during Greenidge's time, Sri Lanka were minnows, you should remove them if you are going to remove Bangladesh/Zimbabwe for overall averages.