Groundbreaking albums. Any genre.

Not necessarily the very best but those that opened up a new direction and influenced many.
Miles Davis - Bitches Brew
John McLaughlin with Mahavishnu Orchestra - Inner Mounting Flame
Pink Floyd - Dark Side Of The Moon
Dead Can Dance - Spleen and Ideal
John McLaughlin/Paco de Lucia/Al di Meola - Friday Night in San Francisco 
Deep Purple - Machine Head