If you look at Nintendo's official figures, the average number of software titles per system (the tie-ratio), it is often not that high.
3DS sold 72m hardware units to 360m software units = 5 software titles per unit
Wiiu sold 13.5m hardware units to 102m software units = 7.5 software titles per unit.
DS sold 154m hardware units to 949m software units = 6 software titles per unit
The Wii did better, and sold 102m hardware units to 920m software units = 9 software titles per unit
These numbers include games that were bundled with the console at launch. Now considering there are many dedicated gamers who buy way more games than this, it also means there are others who buy even fewer than this on average.
So while a deep and diverse library is no doubt important and critical, the average person often does not buy that many games in their lifetime. So I think you can argue that while a deep and diverse library absolutely helps, it may be even more important to have several exceptional games that people feel they must have. The Wii had this with wii sports/wii sports resort, and others. The switch is on track to have several of these as well, with Zelda BOTW and Mario Odyssey.







