It isn't doing better than the Wii did at all. The Wii was supply constrained the entire first several years of its release. Sony stockpiled the PS4 for longer than Nintendo did the Wii and had a larger launch. That's why the earlier months of sales were inflated. After that the sales actually dropped down as low as around 100 000 a week which is pitiful considering the Wii held up at around the 150-200 000 mark. Watch Dogs is the only reason the sales have peaked again. It only brought it back up to a decent number.
Then there's Japan which doesn't even seem to care. Sony has lost a whole market. That alone drops the sales down massively.
PS4 has nothing that can even get the casuals interested in their system right now. Thats like 3/4ths of the PS2/Wii Market that you are talking about. Even for school children I have doubts that the PS4 will prevail all that heavily. If the last 2 gens have taught us anything, its that video games are becoming ridiculously violent. Parents don't like that, and they know the PS4 is pretty much supported by that violence.
In short, Sony doesn't have what it takes to capture a large market like they've found in previous generations. Graphics are nice, but they are killing the mass market.








