But pundits, pleez note: Whiz wasn't first historically, and it's no runaway favorite regionwide.
At John's Roast Pork, which serves up taste-test winners on Snyder Avenue, the processed cheese sauce isn't even served.
"I'm a cheese eater, sweetheart, and I love cheese, but Whiz is not cheese," says owner Vonda Bucci, 75. "It's a lot of grease and coloring."
"We won't do it. We will not carry Cheez Whiz," said Jack Mullan, 50, co-owner of popular Leo's Steak Shop in Folcroft. And customers never complain.
A recent Philly.com poll asked, "What cheese belongs on a cheesesteak?" and Whiz finished third. American edged out provolone - suggesting a runoff poll to settle the issue - after more than 5,700 votes were cast. (See poll, at right.)
Even Geno's owner Joey Vento, 68, downplays Whiz. "To be honest with you, I've never eaten Cheez Whiz, and I'm the owner," he said. "... We always recommend the provolone. ... That's the real cheese."
The yellow runny goo, though, is the top choice of his customers, the locals as well as tourists, he said.
Ditto at Pat's King of Steaks, where Whiz oozed its way into history, said owner Frank Olivieri Jr., 44.
Originally, the Philly steak sandwich, invented by his Uncle Pat in the early 1930s, had no cheese, he said.
By and by, cheese was introduced. "Customers got tired of eating with or without onions, just like my Uncle Pat got tired of eating hot dogs," Frank Jr. said.
American or sharp provolone? was the original debate, he said.
In the mid 1950s - not long after Cheez Whiz hit the market - his father, Frank Sr., began keeping some by the grill, and telling customers to try it.
"It worked well, it tasted good ... it caught on," Frank Jr. said.
Other places started "impostoring us," he said.
But not immediately.
Patent attorney Stuart Beck, 67, remembers American as the standard for steaks, in the mid '50s and early '60s when he was a student at Overbrook High, then Drexel University.
He ate at places like Larry's on Lancaster Avenue, home of the legendary "belly filler," and recalls being served American at Jim's in West Philly in 1955.
"I knew what Whiz was, because I worked in a supermarket, but it was never offered when you went into one of these places," said Beck, who lives in Wynnewood.
Back then, people even asked for mozzarella, he said.
As Whiz became popular at Pat's, American and provolone went out of favor, and weren't reintroduced there until the mid 1970s, Olivieri Jr. said.
Today, Whiz is "overwhelmingly the favorite" at Pat's, outselling runnerup American by 8 or 10 to 1, he said.
Pat's even has a Whiz warehouse that has 2,500 cases or more, each case containing six big No. 10 cans, according to general manager Tom Francano. About 300 are kept in a restaurant back room.
Where Whiz reigns, it pours.
"You might go through eight, 10 cases a day if you're busy," said Vento of Geno's.
"Whiz is a killer. I think Whiz is the best," said Marc Proetto, 42, owner/manager of Jim's in West Philadelphia. Customer prefer Whiz 2-1 over American, he said.
Calling Whiz a killer conjures up clogged artery jokes. But, in fairness, Whiz - mostly whey, vegetable oil and milk products - is lower in saturated fat than American or provolone. Provolone is second-lowest, but lowest in sodium.
"So American loses," said Althea Zanecosky, registered dietician. "The other two, it's a matter of personal preference."
Whiz can even remove grease stains, according to the book Clean Your Clothes With Cheez Whiz, by Joey Green. (Rub in, let stand, throw in wash.)
American takes the biggest slice at many other places - even another heralded South Philly spot, Tony Luke's on East Oregon Avenue.
Owner Tony Luke Jr. confesses, though, he loves Whiz.
"To me, it's always been Cheez Whiz," said Luke. "... I always say Whiz. I never say American."
Unless you're talking chicken cheesesteaks - what Hillary Clinton ordered at Bocella's in Conshohocken on primary election day.
"With chicken steak, it's always American," Luke said. "I won't eat a chicken steak with Whiz."
At Big John's in Cherry Hill, American is consumed six times as often as Whiz, and provolone is No. 2, said general manager Rebecca Ryan, 31.
Provolone is far and away No. 1 at the White House Sub Shop in Atlantic City, which doesn't even offer Whiz.
It's a split decision at Steve's Prince of Steaks. "Honestly, it's about 50-50," said owner Steve Iliesecu, who has two locations in the Northeast, one in Langhorne, another coming in Cherry Hill.
Some customers even order "combo" cheese - a mix of Whiz and the pourable American he invented in 1980, he said.
"American is probably a more legit representation what of mass-market eaters choose in town," said Inquirer restaurant critic Craig LaBan. "Provolone is for aficionados, extra-sharp for the most discriminating among them."
"The whole Whiz thing is overrated," said WIP midday cohost Glen Macnow, who had provolone during his "ultimate cheesesteak" search, won by John's Roast Pork. "The advantage to Whiz is that, because it's runny, it spreads throughout the sandwich," he said. "But a good grill man should know how to melt and distribute American or provolone so that it infuses every crevice."
But Whiz does have its staunch defenders.
"It drips off the steak and mixes with the steak," wrote Pamela in a yelp.com discussion. "It's amazing. I'm sorry but I love it. American and provolone do not drip."
"There is something terrible and yet totally wonderful about Whiz on your steak," "food snob" Marissa M. agreed.
Contact Peter Mucha at 215-854-4342 or firstname.lastname@example.org.