"Looking back, a special match was the Wasps-Leicester game in 2007 - one of the most incredible games I've ever seen."
Greenwood paid special tribute to European champions Munster, recalling "a special and defining moment - the try scored by John Kelly in that 'miracle' match at Thomond Park, especially when Ronan O'Gara also needed to kick the conversion.
"It had to go over; then he did it again against Sale, and so while I'm English and naturally inclined to support English clubs, whenever I see a team in red, whenever Munster take the field, the hairs on the back of my neck stand up because you just sense something special is about to happen."
Greenwood admitted he would never have played for the Lions but for his exposure to Heineken Cup rugby.
"I was lucky enough to go on the Lions tour of 1997 as an uncapped player; no way in the world could I have done that without the Heineken Cup. It gave me the springboard, it gave me the ability to play against the best teams in Europe and that helped secure a place for me in the squad.
"I have no doubt that in the next six months, somebody who hasn't played for their country yet will make a name for themselves in the Heineken Cup and find themselves on a plane to South Africa next summer."