My favourite sequential 5 years for music would have to be 1972 - 1976; I can't possibly restrict it to two albums per year so I won't even try.
Here goes :-
1972 Yes - Close To The Edge, Stevie Wonder - Talking Book, Genesis - Foxtrot, Wishbone Ash - Argus, The Doobie Brothers - Toulouse Street
1973 Genesis - Selling England By The Pound, Pink Floyd - Dark Side Of The Moon, The Who - Quadrophenia, Stevie Wonder - Innervisions, John Martyn - Solid Air
1974 Tangerine Dream - Phaedra, Joni Mitchell - Court & Spark, Stevie Wonder - Fulfillingness' First Finale, King Crimson - Red, Barclay James Harvest - Everyone Is Everybody Else
1975 Pink Floyd - Wish You Were Here, Led Zeppelin - Physical Graffiti, Joni Mitchell - The Hissing Of Summer Lawns, Camel - The Snow Goose, 10cc - The Original Soundtrack
1976 Joni Mitchell - Hejira, Steely Dan - The Royal Scam, Genesis - A Trick Of The Tail, David Bowie - Station To Station, Stevie Wonder - Songs In The Key Of Life