Yes. Smash has been a huge series for a long time, so it increasing in sales over its predecessors is perfectly reasonable, especially on a system that is as hot as the Switch is right now. MH World on the other hand comes from a series that has never been big in the west before, and I expected it to outperform earlier titles thanks to the more beginner friendly approach and higher-end graphics than the series had seen before, this was far beyond anything I thought it would sell.

The difference is in the context. Comparing the two directly in regards to playerbase, platforms, and sales is kinda pointless since they come from two completely different places.

Probably part of the surprise is that Smash Bros. Ultimate is not only selling well, but allowed the Switch to move so much hardware that it broke records. Sure, Smash is a system seller, but I don't believe at this level. 1.77 million Switch units were sold in the U.S. during the month of December, the highest amount of units in a month sold in this generation, especially considering that the Switch did really well in November and that the PS4 has dominated this generation but has not been able to post even these kinds of numbers during the holidays.

True but taking in to account that(if I am not mistaken) December is always the biggest sales month for Nintendo. Added with the hottest new gaming until being the Switch and the biggest Nintendo release in history the sales add up pretty well for December. Has Sony ever REALLY been "big" in Dec like Nintendo? I am genuinely asking because I don't know for sure. But from my memory I don't ever remember it being.

Yes, I agree.

Still someone predicting 15M shipping (not really saying 12M sold or anything the like) and it selling 15M shouldn't qualify as the most exceeding sales expectation right? When MHW where past 10M when several expected like 1M, 3M at most.

Sony and MS where a little bigger in Dec in the past, but with BF many sales migrated to Nov.

Only one person who made that bold prediction while the others weren't.

About MHW situation, the signs were there when the E3 trailer is the most watched trailer for Capcom game and the stage presence at E3 was the biggest for the company. Combined with a multiplayer aspect of MHW there wasn't a single doubt about MH was about to explode in the western market especially with capcom largest marketing push ever recorded. The only skepticism was in the Japanese market where it was ditching the portable for a stationary console, and they managed to sell it really well then from there MHW was going to break Capcom sales record for the WW market. 

The ones who keep downplaying the sales were fanboys who couldn't accept Capcom decision to change from portable console to stationary consoles and also with the underperforming titles like SFV, RE7, and MVC didn't help with the perception of Capcom strategy. 

I think people still had doubts about the Switch coming into December, especially when they had the lofty goal of wanting 20 million units shipped by the end of the fiscal year. Despite Smash Ultimate being the biggest Nintendo release of the year (maybe ever), there were still doubts that it could do the kind of numbers we saw, especially when people believed Nintendo lost some momentum throughout the year because of their relatively quiet first half of 2018.

As for Sony and Microsoft, yea I think they've aimed towards getting more sales in November and utilizing Black Friday. But still, with Sony selling the way it is, you'd think it would have sold more than 1.77 million units in a month, especially during its peak years.

Here is a PS4 breakdown of November and December. (and October bonus)

2013:

Nov: 1.14

Dec: .86

2014: 2.20

Oct: .300 (13.6%)

Nov: .83 (37.7%)

Dec: 1.07 (48.6%)

2015: 3.40

Oct: .280 (8.2%)

Nov: 1.54 (45.3%)

Dec: 1.58 (46.5%)

2016: 2.905

Oct: .235 (8.1%)

Nov: 1.1  (37.9%)

Dec: 1.57 (54.0%)

2017: 2.865

Oct: .205? (7.1%)

Nov: 1.58 (55.1%)

Dec: 1.08 (37.7%)

2018: 2.638

Oct: .340 (11%)

Nov: 1.478m (56%)

Dec:  .820 (31%)

December 2018 was abnormally low and October was a bit higher. Overall is down due to December. Sony has big holidays whenever it's December is also big.

SMP is above my expectations, GOW below.
The rest are kinda in point to them.

I guess you weren't in the threads them. MHW is much much much above what was being predicted and it wasn't just a small number of people that expected low sales. While Smash had very high expectations, you can say it exceed it, but to say it is the game that most exceed is another thing.