Van Morrison - Astral Weeks & Moondance would be the conventional pick (and it's one that works) but I prefer Tupelo Honey & Saint Domenic's Preview
The Band - Music from the Big Pink & S/T
Nick Drake - take your pick
Rolling Stones - Let It Bleed - Sticky Fingers - Exile (whichever pair you prefer but I'll go sticky & exile)
Neil Young - take your pick of any pair from "Everyone Knows This is Nowhere" Through "Zuma"
David Bowie - Ziggy/Aladdin Sane
Dylan - Bringing it all back home, Highway 61 Revisited & Blonde on Blonde - take your pick of pairs
Curtis Mayfield - Curtis/Superfly
Aretha Franklin - Lady Soul/Aretha Now
Leonard Cohen - Anything from late 60's through 74 but I'll go with "Songs of Love and Hate" and "New Skin for the Old Cemetary"
Stevie Wonder - take your pick of late 60's through early 70's
Archie Shepp - "Attica Blues" & "the Cry of My People"


I could go on and on. Its not hard to find two great albums back to back. Five or more seems to be the more rarified air.