The Mario hack series goes probably as high as 16
games. That is, the first three -- Super Mario
Bros. through Super Mario Bros. 3 -- are
the licensed games, whereas the hacks follow,
starting at Super Mario 4. That's a total of 12 games in the
Mario hack series, but there are many, many other
Mario hacks beyond the series, such as Somari:
The Adventurer, a Sonic the Hedgehog port
with Mario taking the place of Sonic.

The "16" was written with a black marker.
I have no doubts that when "16" was written
in black marker on
the label for this game, it was done by the maker
prior to its distribution. To me this says the maker
fudged the label by only calling it "Mario Bros.,"
which wouldn't be a big seller, and had to add the
"16" to make the game more attractive and
jive with the start screen. Why not just
print new labels? Simple...that would waste precious
money.
There have got to be about 50 or so games that
have Mario hacked into them. Some of the hacks were
successful, meaning the gameplay is smooth, even
with the new sprites. But some fail, like Super
Mario 4, a hack of Armadillo and the
first of the series. When it comes to buying Mario
hacks, it's hard to discriminate, because even the
ones with ridged gameplay are fun to see.

Mario Bros. 16's start screen.

"Best Cavemen" must a remnant of the hacked game.

A caveman prepares to club Mario.
Mario hacks sometimes don't sell for nearly as
much as I think they're worth. They typically go for
about $10, but they're often hard to come by and
should sell for about $25 a piece, in my opinion,
especially the ones with great gameplay.