Square Enix has ranked their franchises in order of their perceived selling power in their 2009/2010 fiscal year report, outlining what franchises are more likely to see more games produced in the process.
The ranking lists Final Fantasy, Dragon Quest and Kingdom Hearts as the top-selling franchises in that order. They're followed by a string of Eidos franchises - Tomb Raider, Hitman, Kane & Lynch, Deus Ex, and Just Cause.
Parasite Eve, Front Mission, Soul Eater and Star Ocean all put in appearances further down the list. Check out that page of the presentation below. Click it to make it bigger!