Don't most bands put out great LPs back to back? You could make an argument for any of these:
Radiohead -- The Bends / OK Computer /Kid A
Husker Du -- Zen Arcade/ New Day Rising / Flip Your Wig
Rolling Stones -- Beggars Banquet / Let It Bleed / Sticky Fingers / Exile on Main Street
The Stooges -- self-titled / Fun House / Raw Power
Springsteen -- Born to Run / Darkness on the Edge of Town / The River / Nebraska
Bad Religion -- Suffer / No Control / Against the Grain
X -- Los Angeles / Wild Gift / Under the Big Black Sun / More Fun in the New World
Sonic Youth -- EVOL / Sister/ Daydream Nation
The Who -- Sell Out / Tommy / Who's Next / Quadrophenia