The way I see it at the moment, there's a very region specific market at play here.
The North American market is far more focused on first person shooters, sports games, and action, and while Americans tend to cream their pants like it's going out of fashion when someone mentions the Nintendo 64, they really haven't given a shit about Nintendo since 1998 if we're honest. North America will remain a battleground between Sony and Microsoft. Generally there's a preference towards Microsoft evident in this region and I think in the long run the Xbox One will outsell the PS4 in North America by a small margin. The Xbox Live community is strong. Halo is still a system seller. Games like Destiny and Titanfall will see more people buying. I think the boom for the Xbox One will be the last half of 2014 as there's still plenty of people who are, "waiting for some decent games to come out". In the end though, by 2016 I wouldn't be shocked if most North American gamers have both the PS4 and Xbox One so I'd put Microsofts lead as minimal but still present. The Wii U figures in North America will likely match those of Japan but considering relative population, that will put Wii U in a trailing last place.
The Japanese market is pretty much a split market. There's the Sony and Nintendo markets and they seem to have little effect on each other. You cannot get a Japanese person to buy an Xbox product without threats of torture, so the Xbox One will fall flat on it's bloody face over there. It's not even close to competitive. The PS4 will sell well, probably on par with the Wii U as they will be offering different experiences. Add in the earlier release schedule for many games, lack of recession issues in Japan compared to other regions, near non-existent PC gaming scene compared to other regions, and relatively low prices for games/consoles, and it's again most reasonable to presume that many gamers will have both a PS4 and a Wii U. One thing that would boost Wii U sales is an add-on that would allow DS/3DS games to be played on the console. The Japanese would eat that up.
As for the European market, welcome to economic crisis central. Greece, Spain, Italy, Ireland; these are all countries that are defaulting on national debt and have the worst economy in decades. UK, France, Poland, Netherlands. Not all that far behind. The only countries doing OK are Denmark and Germany, and they're hardly rich at the moment. Couple that with companies that don't have the faintest fucking clue how exchange rates work and you have a Europe that cannot afford to game. Seriously, a game here currently costs $92US, so America has it cheap at $60. The consoles have the same problem. Removing "$" and replacing it with "£" or "€" is not how exchange rates work. So, as you can imagine, there's a far larger rental and pre-owned trade here in Europe. Microsoft basically signed their death warrant when they said they where banning used games, even reversing that policy is no good now as no-one will trust them. Couple this with the Xbone being pushed as a "multimedia" device where you can watch USA-only streaming service, USA-only streaming service, USA-only pay per view service, and for a change of pace, USA-only streaming service; and you end up with Europeans being completely disinterested.
Interestingly enough many Europeans are refusing to upgrade, sticking with PS3/360 and their PC's until something worthwhile comes out, so while the PS4 is doing fairly well, I'd expect it to sell consistently for a while as many European gamers cannot afford a console at launch without saving. That said, those who can again, tend to buy multiple consoles, so I'd expect to see the Wii U get the "second console" position, which means it will likely see more sales by 2016 as the prevailing attitude is "I want a Wii U, but I can only afford one console this year".
One last thing to consider are the outlaying regions. Australia/New Zealand isn't tracked properly, and it has an interesting mix of European and Japanese tastes when it comes to gaming. It may not have a massive effect but it's something to consider. Same with Brazil, it's a massive region, but with tax and import laws as they are now, new consoles (both PS4 and Xbox One) are costing equivalent to $2000+ which is quite frankly ridiculous. The first company to put significant production in Brazil however will be able to bypass many of those costs and gain government subsidies; they can then significantly lower their prices, and effectively claim the region uncontested.
Lastly, there's India, which up until recently was ignored. Outside of limited release and importing, India has no official region consideration as a gaming market until now. Sony is planning a full nationwide release in India for the PS4 next week, January 6th 2014 for ₹40,000 which is about $650US. That's actually quite reasonable considering the 37% consumer electronics tax in India. This release could effectively cause Sony to claim a new regional market entirely uncontested, and it's a region who's population dwarfs even the North American market. If this move works out for Sony, the PS4 will hands down win this generation.
Summary:
The PS4 will win the generation, with strong sales across the board. It will have market dominance in Europe, Australia, and India and a strong ~40% market share in Japan. In USA it'll be close second, but with enough third party support that it may overtake Xbox One by the end of the eighth generation.
The Xbox One will have a strong following in USA and will remain the de-facto home for FPS gamers with Halo, Titanfall, and even Call Of Duty/Battlefield/Destiny (despite being multiplat), because of Xbox Live. Outside of the North American market it will be a distant third place, particularly in Japan where it will likely be discontinued by 2018. Microsoft is however the most likely company to move some of it's production to Brazil given Sony's financial situation, so may claim the Latin American market. If so, the Xbox One may still be a success.
Wii U will sell well in Japan, likely having the largest market share, and will have a decent following in Europe as the default second place. Globally however it will be the third place console, with poor sales in North America, no movement into additional markets, and a lack of third party support. It will likely be perceived in a similar vein to the Gamecube, however 3DS sales, and strong first party software will ensure that Nintendo remain profitable, although there is a risk that many, perfectly decent Wii U games will be denied localisation outside of Japan.
This generation will be a battle for second place between the Xbox One and the Wii U.
Let me know what you think of my analysis and opinion, if you agree or disagree and why. I'm no industry expert so my opinions are subject to change if people have information I've not considered.
