In America
If you have the name in the title, it counts as part of the franchise. If you don't, it doesn't.
1. Mario - 177.4M
2. Pokemon - 65.2M
3. GTA - 38.8M
4. Madden 36.9M
5. The Sims - 33.4M
6. Tetris - 32.8M
7. Zelda - 26.3M
8. Sonic - 25.9M
9. DK - 22.1M
10. Crash Bandicoot - 19.1M
11. FF - 18.5M
12. GT - 18.3M
13. Halo - 17.5M
15M + sellers only for America ATM
Japan:
1.Mario - 80.5M
2. Pokemon - 51.4M
3. DQ - 38.8M
4. FF - 30.7M
5. DK - 14.2M
6. Kirby - 11.3M
7. Zelda - 10.4M
Others:
1. Mario - 71.4M
2. Pokemon 45.6M
3. GTA - 33.4M
4. GT - 22.3M
5. The Sims - 22.1M
6. Fifa - 21.8M
7. Need for Speed - 19.4M
8. Pro Evo - 19.3M
9. Sonic - 17.8M
10. Crash Bandicoot - 15.7M
11. Zelda - 12.1M
12. FF - 11.4M
13. Brain Training - 10.9M
14. Nintendogs - 10.1M
15. Tekken - 10.1M
Okay, the lists are very incomplete. Any lacking data would be awesome if added. I'll add total later.