I like your arguments, but TTG most succesfull game may have been TOMI.
BttF is confirmed to be the most successful TTG game, at least by Q1 2011.
And there's also information that TellTale's revenues in 2010 were 90% greater than in 2009 (which is the year when ToMI was released and when it would be sold the most). Although, admittedly, 2010 saw both S&M3 and BttF. (But, 2009 had Wallace & Gromit and ToMI).