50 marketshare doesn't matter for another reason.

Marketshare is important because it shows how dominant you are in the market. The more dominant you are, the more free exclusives you're going to get from multi developers.
And since wiiu has already been excluded from most developers it's not true that ps4 is at 50 per cent marketshare.

It's actually almost at 65%, because wiiu doesn't count anymore.

Ouch. 

If anything, it only points to the Wii's short legs that it never achieved 50%.  The other consoles only really hit their stride in the 3rd year, which also just happened to be the peak year for the Wii.  The Wii was able to bring a new customer to console gaming, but hardly any of them stayed.  In the end, it really had little impact on how we play games.

And the PS1 and PS2 both had 50%+ by default.  Was gaming in a sorry state, then?  Or was console gaming still alive and well, and those consoles were just seen by the majority to offer the best bang for your buck?  I'm going with the latter.  Same goes for this gen.

Don't you think it would be smart to see how high PS4 can jump, and possibly how low XBO can fall, before judging how much "far better" is?

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SALES
Launch	3,000,000
Year 1	17,000,000
Year 2	24,000,000
Year 3	21,000,000
Year 4	17,000,000
Year 5	11,000,000
Year 6	5,000,000
Year 7	2,000,000
Year 8	500,000

Well, this is the Wii yearly sales. The firsts 3 years are too much for PS4. By year 4 (2010) MAYBE PS4 have a chance... but i don't think so. I think PS4 will break the peak in 2016 (so, year 3), and will sell around 17,000,000 this year. (2016). Still, not a Wii level (21,000,000)... by year 5 (2011) i can see PS4 sell more... but will not close the gap with the firsts 4 year, so, i don't think will pass Wii in lifetime sales... we will see!

All these Wii sales numbers just make it that much sadder when you think about how WiiU is doing. You can just about divide it by 10 and get the current sales.
From market leadership and almost domination to almost complete irrelevance.

First @OP: Why do you omit european and worldwide sales?

Secondly: While the Wii-sales were crazy, they died down pretty strong after the high. PS4 might have a more normal console cycle. That's why PS2 sold 50% more than Wii.

Third: 50% are important as PS4 manages in overall smaller console sales strong numbers.

Fourth: As kowenicki already pointed out, the Wii was an anomaly in the meaning that despite it being winner of the gen the PS3 and X360 still sold strong. It may point out, that the Wii sold to a separate demographics in part, that may be a reason why we see a decline again in this gen in overall console sales.

Overall I think the PS4 might reach the 100M of the Wii but probably not the 150M of the PS2 at the end of it's life. But I might be wrong on this.

And because it's only $299.  Can't wait to see sales after $199, as well.  People think its an unfair race, now, it'll be a slaughter.

Seem legit...

Well, I don't know why 50% marketshare is that much of a deal. PS4 is still selling two times less than Wii in the same timespan, the real difference here is that PS3 and Xbox 360 picked up a lot of steam as time went by and ended up selling 80 million each. Right now, 50% marketshare is easy to reach because of how poor Wii U and Xbox One are selling.

So, with that said, I'm not really impressed with the performance here.

But ps4 dominate it's competitor unlike Wii.