Rolling Stones - Goats head soup - It's Only Rock N Roll (most would say Exile and Goats Head I'm sure)
Jethro Tull - A Passion Play - War Child
(I never minded A Passion Play much, but War Child completely lost me, and my interest in them went down the shitter for me)
Weezer Pinkerton - Green Album
Kinks Muswell - Everybody's In show Biz
Ween Quebec/Shinola (basically a compilation of outtakes) - La Cacuracha
Definitely Smile Smile and Who By Numbers. I love those albums but they're definitely a downgrade from their predecessors either way.