In its recent financial report, Ubisoft published a chart of the top 20 best-selling game franchises of the past nine years, and the results were interesting.
These numbers represent the cumulative console retail sales of all games in a given franchise on the last two generations of systems and PC (Xbox 360, PS3, Wii, Wii U, Xbox One, PS4, and PC).
1. Call of Duty
2. Mario
3. FIFA Soccer
4. Assassin's Creed
5. Grand Theft Auto
6. Wii Fit (includes hardware)
7. The Sims
8. Madden NFL
9. Guitar Hero (includes hardware)
10. Battlefield
11. Halo
12. Need for Speed
13. Just Dance
14. World of Warcraft
15. NBA 2K
16. Lego
17. Sonic the Hedgehog
18. Rock Band (includes hardware)
19. Elder Scrolls
20. Gears of War
[Source: Ubisoft via Destructoid]
Our Take:
This is a really interesting list. Obviously, no surprise at number one. However, despite the perception that Mario is fading, he's still holding strong (by the way, where are the other big Nintendo franchises?). His old rival Sonic is still doing well, too. 
It's also impressive that GTA and Elder Scrolls are where they are given how many titles some of these other franchises. Finally, it's an indication of the risks of the game industry when you see that two of these games, Guitar Hero and Rock Band, are now completely defunct and unlikely to return.
Reference GameInformer