I have stayed at.....

Desert Inn
Sands
Dunes
La Mirage (not THE Mirage)
IP
CP
MBay
Luxor
LVC
Nugget
Fitzgeralds
Barbary Coast
Maxim
Bourbon St
Stardust
Westward Ho
Harrahs (Was holiday Inn then)
Riveria
Sahara
Hacienda

ETA: Rio, MSS

I think that's it

Aladdin (the original)
Mirage
Barbary Coast
Harrah's
Caesars
Bellagio
Wynn
Encore
Green Valley Ranch
Four Seasons
Rio

Great idea for a post. First went to Las Vegas in January 1992 and have been hooked ever since. Half the fun was checking out different hotels. Now as an aging Baby Boomer, I just stick with Boyd properties. In no particular order, I've stayed at...

Bally's (my first)
The old Aladdin
Sands
Sahara
Stardust
Excalibur
MGM Grand
Luxor
Mandalay Bay
San Remo
Barbary Coast
New York New York
Monte Carlo
Flamingo
Harrah's
Caesars Palace
Treasure Island (Got married there when "Con Air" was being filmed across the street at the closed Sands. I remember the plane was sticking out of the lobby and our Maid of Honor met Nicholas Cage. Very cool!)
Stratosphere
Rio
Gold Coast
Orleans
Palace Station
Golden Nugget
Lady Luck
Fremont
Main Street Station
Suncoast
Finally, there was a hotel west on Flamingo and across the street from Bally's that I stayed at in the mid to late 90s. Can't think of the name and it's driving me crazy. Any ideas?

Would that have been the Dunes? (Where Bellagio is now.)

Treasure Island
Luxor
Fitzgeralds
Rio
Paris
Mirage
Aria
Bellagio

Hacienda
Imperial Palace
Tropicana
The New Aladdin
Sahara
Paris
Ballys
Caesars Palace
Rio
Planet Hollywood
Sunset Station
Aliante Station
Green Valley Ranch
Red Rock
Wynn
Circus Circus - when I was a kid - the one and only time my parents brought their kids to Vegas

Stardust
Rio
Ballys
Flamingo
(Since RIO has been my favorite for years, I have mostly
stayed there.) Love the vibe there, the cool wine bar, and
the Voodoo Lounge on the 51st floor with outdoor terrace!

Alladin (first time ever)
Planet Hollywood
Paris (most times on strip)
Treasure Island
Sands (worse room ever)
Gold Coast (probably the most times)
Ballys
Flamingo
Orleans
Bellagio (within the first month of opening)
SouthPoint (current favorite)
M (great rooms, rest of the casino and service headed south)
Luxor
Mandalay Bay (probably my wife's fav)
Wynn (best room ever)
Golden Nugget (only venture downtown)
Frontier (good Mexican restaurant in the day)
Bob Stupak's Stratosphere (remember those deals they used to have)
Tropicana (mirror on the ceiling)
Imperial Palace (got married in Vegas and stayed here...it used to be decent many years ago)
Harrahs
Maxim (last minute decision, all I could get)
Ceasars (hot tub room...good memories)
Rio (20% of trip spent waiting for an elevator)
Fiesta (obviously had a car)

Excalibur (3 times long ago)
Harrahs
MGM
San Remo
Golden Nugget - 2 times - Once in Gold Key Floor Suite - Very Nice Room
Monte Carlo (7 times - Great Host)

Very short list for this low roller:

Palace Station
Planet Ho
Lady Luck
Golden Nugget
Plaza
El Cortez

So we can assume that nobody here has stayed at the Western and lived to tell about it?