I pretty much agree with Mitch.
Pink Floyd: Wish You Where Here. While there are some great songs ? sides even ? on The Wall, the 4th side just doesn?t do it for me. (I still have it on vinyl; got it for my 13th birthday.) Dark Side is good, but not as thematically focused as Wish You where Here.
The Beatles: While St. Pepper?s is of greater historical importance, I prefer Abbey Road. The second side just rocks and as Mitch says, it holds up better four decades later.
The Who: Tommy over Quadrophenia. Neither though is as strong as Who?s Next, which is just an amazing collection of songs.
The Stones: Pretty much a push between Sticky Fingers, Exile on Mainstreet, and Let it Bleed. Overall, might have to go with Exile. It?s all very dark stuff though ? you won?t fully appreciate until you’ve heard it at 3am when you?re in your darkest mood over a girl (guy), drinking whiskey straight, and then you?ll see exactly where the Stones were coming from and why people talk about the light of the Beatles vs the dark of the Stones.
Led Zeppelin: I over IV and II. I like their hard blues. Physical Graffiti is overrated.