There are countless factors in a deck's success.
Quality of the art.
Originality of the theme - or lack thereof! An unoriginal theme can succeed if you do it better than the decks that preceded it.
POPULARITY of theme.
MARKETING, MARKETING, MARKETING - it can't be emphasized enough.
Quality of manufacture - it can make a difference, depending on the actual design. Sometimes printing matters more than stock. Sometimes packaging makes the difference.
"Bells and whistles" - bonus features like foil, metallic ink, embossing, custom deck seals, unique box design, etc.
In the end, there's too many factors to boil it down to a simple formula guaranteed to succeed. But with a bit of research, you can, with the right elements, make a successful deck. Many have - so can you. Some have even made a successful business model out of it. Just don't imagine for a moment that getting the design thought out or just making cool artwork alone is enough. It's work from start to finish.