Install base won't play a huge role in sales, for example...
Sonic Colors (2010/Wii): 1.56 million
Sonic Colors (2010/DS): 1.19 million (larger install base)
Sonic & Sega All Stars Racing Transformed (2012/3DS): 200,000 (larger install base)
Sonic & Sega All Stars Racing (2012/Wii U): 300,000
Lego City Undercover (2013/Wii U): 700,000
Lego City Undercover (2013/3DS): 930,000
Sonic Lost Worlds (2013/Wii U): 180,000
Sonic Lost Worlds (2013/3DS): 260,000