"Just like downtown” is a saying that became popular in 1949-1950. “Downtown” means the place of excitement, where the lights are bright and there is shopping and entertainment. “Just like Downtown” (1954) was a song by Jimmy Work.
“Just like New York” was sometimes said instead of “just like downtown.” The term “just like New York” was not used in New York City itself, but appears to have been popular in Indiana and Illinois.
Michigan Vocational Outlook
Just Like Downtown!
12 June 1950, Rockford (IL) Register-Republic, pg. 10, col. 1 ad:
And, thanks to the easy-to-clean smoke-proof, fire-proof Whirlpool broiler pan, you broil everything “just like downtown.”
(Universal Gas Range.—ed.)
26 June 1950, Canton (OH)
EXTRA in broiling
A gas flame gives you a smokeless broiler as the flame burns off the smoke as it is formed, giving chops and steaks that extra flavor; “Just like Downtown!”
(Suburban Gas & Appliance.—ed.)
OCLC WorldCat record
Just like downtown
Author: Jimmy Work
Publisher: Gallatin, TN : Dot, 
Edition/Format: Music : 78 rpm : English
23 October 1961, Rockford (IL) Register-Republic, pg. 12 ad:
“JUST LIKE DOWNTOWN”
Downtown has long been known for its standards of efficiency, up-to-dateness, and quality. So much so that it has become a by word in the phrase “Just like Downtown. Downtown stores always have the latest in styles for the fashion conscious shopper.
Remember...when it’s the newest
the most modern
“Just like Downtown”
Chicago (IL) Tribune
Everything Must Go
As America’s Oldest Department Store Holds Its Final Sale, A Wisconsin Town Says Goodbye To A Member Of The Family
July 18, 1994|By Ron Grossman, Tribune Staff Writer.
The phrase “just like downtown” used to be shorthand for first class. A generation ago, Schuette’s was rivaled by a Sears store, a Penney’s, a Boston Store, a Kresge’s and a Woolworth’s. Those other businesses are long since shuttered, and empty storefronts and deserted streets make Manitowoc seem a ghost town after 6 p.m.
July 17, 2009
“What does the phase “Just like downtown mean”?
It’s pretty self-evident, isn’t it? It’s a statement of quality, comparing goods or services of modest background (originally, something rural or small-townish) to the top-of-the-line stuff that, back in the day, could only be gotten in the top shops of whatever city—aka “downtown”—was closest at hand (or comparing something to that which was only enjoyed by those living downtown). Basically, it’s a take on “the real McKoy” expression, only with a geo-class perspective.
JIMMY WORK Just Like Downtown
Uploaded on Jul 28, 2010
“Just Like Downtown” by Jimmy Work (Google Play • AmazonMP3 • eMusic • iTunes)
American Dialect Society listserv
“It’s just like New York”
David A. Daniel dad at POKERWIZ.COM
Wed May 2 17:54:41 UTC 2012
I’ve never heard that, but it could be an east coast thing. I’ve often heard, but rarely used, “Just like downtown” to mean something done well or correctly or something supposed to be of high quality. The Google hits I read re New Yrk seem to be literal.
Poster: “Joel S. Berson”
Subject: Q: “It’s just like New York”
“It’s just like New York”—does anyone think of this phrase as meaning that something has been done well or correctly, or some similar meaning?
A Way with Words
Just like New York
Posted by grantbarrett on February 20, 2015
An Indianapolis listener is curious about a saying his dad used to describe anything that’s excellent or the best of its kind: Just like New York.
February 24, 2015 at 1:00 pm
My father uses a phrase very similar to this. Whenever a project or a measurement goes even better than expected he exclaims “Just like downtown”. It is a positive exclimation, and I have nearly exclusivly heard it used in construction jobs. He is an electrical engineer by trade, just turned 65, and hails from the hills of San Fransisco, working volunteer construction in his retired free time.
Ed Foster says:
February 26, 2015 at 6:56 pm
In a neighborhood where I lived on Chicago’s North Side, there was a janitor who used the phrase “Just like downtown” to mean the same as “Just like New York”, which I heard for the first time on this program. This was in the 1970s, and the janitor had been a radio announcer at some time in the past.