"There's no way it can sell to xx% of the userbase!"
Going by VGC data...
Super Smash Bros Melee (JP):
360k first week on 475k GC's (76%)
Halo 3 (America):
2.84m first week on 7.64m X360's (38%)
Final Fantasy X (JP):
1.91m first week on 5.17m PS2's (37%)
Final Fantasy VII (JP):
2.03m first week on 5.23m PS1's (39%)
Some interesting first month sales...
Gears of War (America):
1.32m first 4 weeks on 3.97m X360's (33%)
2.10m first 8 weeks on 5.08 X360's (41%)
Mario Kart 64 (JP):
1.06m first 4 weeks on 1.71m N64's (62%)
Pokemon Ruby / Sapphire (JP):
2.43m first 4 weeks on 4.01m GBA's (61%)
3.70m first 8 weeks on 4.94m GBA's (75%)
Remember, these games also move quite a few consoles, which makes the attach rate a bit lower. For the multiple week sales, I took the final totals of the userbase (when Pokemon R/S came out, GBA was at 3.8m).
