This is only for home console.
These are the sales for the past FF main game
FF VII: 9.7 M FF VIII :7.86M FF IX: 5.30M FF X: 7.95M FF X-2: 5.21 M FF XII: 5.67 M
And this are the sales for other RPGs
Xenogears: 1.20M Valkyrie Profile: 0.7 M Valkyrie Profile 2(Japan only):0.39M Suikoden series (1 to 5): 2M Lunar 1 (Sega + PS1): 0.6
Wild Arms series: 1.5M Tales Of ..... series: 10 M for 20 different titles (and average of 0.5 M per games) Legend of Dragoon: 1.86 M
Shin Megami series ( japan only): 1M
For this new generation:
Dragon age: 0.91 M on Xbox360 and 0.45 M on the PS3
Lost Odyssey 0.80 M
The best selling RPG on the Wii: Pokemon Battle Evolution: 1.43 M
To make matters even more astonishing:
Total RPGs on the PS3 in Japan (for 19 games including FF XIII): 3.18 M and FF XIII: 1.50 Millions representing: 47% of RPGs sold in Japan in only 5 days.
Total RPGs on the PS3 WW: 8.57 for 23 games and FF XIII percentage in 5 days: 17%
The only exceptions so far are: Fable 2: 3.31 M and Elder Scrolls 4: 2.89 M both on the Xbox360
Edit: And Fallout 3: 2.82 M and Mass Effect: 2.10 M
This means to me that there are a few RPG fans, but a lot of FF fans
Essay Pro