C64 in north america was ubiqitous and probably one of the first network effects. My friends Zach and Josh and traded games back and forth effectively doubling their game library. Quality was superiour to the 2600 and the NES wouldn't be out for a few more years. definitely a sweet spot.

The killer app for a high school kid was a word processor and printer. Really couldn't do that with a dedicated console. Teachers were inclinded to give better marks for typed content that obviously easier to read than the chicken scratch that passed for cursive. With spell check, that was the ultimate cheet code.