I immediately thought of Arena Rock bands. That style music began in the 70’s. Linda Ronstadt was the queen of Arena Rock - As a solo artist.
Arena Rock Bands were known for outstanding Live performances. They charted hits but it was their live performances that made them great.
Journey
Styx
Boston
REO Speedwagon
So Journey, Styx, and Boston. 
Honorable mention for REO Speedwagon. 
My first three are the biggest 70’s arena acts.
I value great live acts. Bands that went out there night after night and Entertained people.
With no deliberation: Who, Stones, Floyd. With a second of deliberation, I can see Zeppelin replacing one of them.
I should know better, but based on what criteria?
This doesn’t seem remotely correct.
(I threw in four extra underneath myself …)
Aerosmith
Kiss
Pink Floyd
Lynyrd Skynyrd
The Allman Brothers Band
The Marshall Tucker Band
I wasn’t of an age to pay attention to music in the 70s but growing up in the South, these were the bands that were played endlessly in the background of every barbecue shack, pool hall, dive bar and other establishment.
Led Zeppelin
Queen
ABBA
Led Zeppelin
The Eagles
Fleetwood Mac
True, and I remember being so cool that we never said the full name of the bands that we’d hear late at night on the “underground” stations (that ignored the Top 40 and played albums, man…).
Zep’lin
Floyd
Tull
I’m trying to keep in mind that “the 60s” ended about '72 or so, so the early 70s were still Nixon, hippies vs the straights, Vietnam protests, Watergate, and the music was much more “protest-y”. Mid-to late 70s was lighter, more optimistic.
That’s why we’re getting bands as diverse as Pink Floyd and REO. Different eras, even if in the same decade.
So I picked 1970, when I was in high school.
Led Zeppelin
Mahavishnu Orchestra
X
X- American, or Australian?
Sex Pistols
Donna Summer
Foghat
Here’s a list of Arena rock bands. The four I listed are the ones my friends and I would have driven 150 miles, from my small town, to the city to see.
AFAIK they sold out consistently. I didn’t research ticket sales for arena rock bands.
I debated between Aerosmith and Foreigner. They were both extremely popular when I was in school.
The Beegees, Eagles, and Chicago.
Led Zeppelin
Fleetwood Mac
Boston
And also that the OP can be interpreted as best vs most specific vs most quintessential, and that there were several types at the same time that were very ‘70s - arena rock; brass driven; progressive…, and how old we each were, thinking of high school or college or other, each of which may have had other musical exposures …
I think asking ‘60s or ‘80s might also give a diverse collection.
It’s hard to think of a period with more diverse music.
Singer-Songwriter Neil Young,Croce,John Denver
Various generes of rock
Punk
Disco
Metal
Pop
Outlaw Country
Classic Country
They all sold records and charted hits. The 70’s was a great time to grow up and listen to music.
It’s hard for people today to understand George Jones,Charley Pride, Marty Robbins were charting hits at the same time as Waylon Jennings, David Allan Coe and Willie Nelson.