According to Brand Finance (who run the site BrandDirectory.com), the Mets were the 64th ranked sports brand worldwide for 2012.
The site rates the Mets with a Brand Value of $145 million, and a Brand Rating of BB+ (anything in the B-BBB range is considered average)
As a point of comparison, the Yankees ranked 10th globally with a Brand Value of $398 million and a Brand Rating of AA. The top NL club was the Cardinals at 37. Overall the Mets ranked 10th among all MLB franchises – just ahead of the Angels and behind the Reds (yes, the Reds).
(I’m sure Howard Megdal can probably sink his teeth into this a lot more than I can)
The top worldwide brand was Manchester United (not a shock) with a Brand Value of $853 million and a AAA+ Brand Rating.
The full tables (which can be segmented by country) can be found here
Interesting that the Mets sit there with the White Sox and Angels– two other “second” teams in their cities.