Such a hard choice..
Several that come to mind:
The Silver Jubillee airshow at Finningley in 1977 where the Harriers performed their "bow" to the crowd for the first time, and also the 4-ship Vulcan scramble
The Belgian "Slivers" at Alconbury - a pair of F104s in fast head on passes with very little apparent room to spare.
The Red Arrows "Twinkle Roll" in the early 70s.
Adrian Gjertson in G-HUNT at the Fenland Air Show in about 1980 - low and fast and kicking up a maelstrom of hay from the straw bales around the spectator area!
So many good memories.
The 60s and 70s were certainly golden times for airshows, but the kids that saw the RAF at homes and Empire Day displays in the 30s might disagree about them being the best!!
However, although the variety of military machinery has diminished at todays airshows, we still get a fantastic variety of aircraft and I want to thank each and every display pilot for their art in showing these wonderful machines to us.