Well, then let's bet on it. If it sells over 1.2 million, I win. If it doesn't sell 1.2 million by the end of 2016, you win. Loser has to change their avatar to a picture of their mom for a month.

To answer the OP:
#1, This is predominantly a Nintendo site.
#2, Nintendo fans are thirsty for a new Ninty IP. Just google search fan art.
#3, First big game of 2015 for Wii-U. (Though MP is no slouch, it sorta came and went.)

There's no reason to believe it'll perform poorly (like Bayo 2 predictably did), but it isn't an established brand. Splatoon will sell very well for what it is.

First, this is a first time ever that I heard for that game.

After little research, both game only could be compared in initial content, Splatoon is Nintendo triple AAA 3D shooter game with focus on online, that only lacs some content on launch, but we already know that more free content is arriving.

So, I cant relly see how you can see Splatoon like a $20 downloadable game.

Oh look, the game is almost completely sold out in Japan.

EDIT: And saying that Splatoon is comparable to Fat Princess is on the border of trolling I would suggest. You think those games took the same man hours? No, you don't, as I say, you're just being a borderline troll.

It seems to me that splatoon will be a game that will create a lot of initial demand from nintendo fans (like pikmin 3), but will drastically die down over a short amount of time. The reviews weren't that good for a new ip. The content is abysmal upon launch and will only become mediocre after all the dlc arrives. The game is priced unreasonably high in the US (the market that actually could have made this game big). And the game is pretty much only marketed towrds kids. Why buy this game over black ops 2 ($20), or team fortress 2 (free), or borderlands collection ($50), or metroid prime trilogy ($20 eshop), or mass effect collection ($5 from flash sale, $25 regularly)? The summer is known for big game sales (check steam), but Nintendo is releasing a half-finished game at $20-$40 more than other proven classic titles. Overall the game should do around 800k-900k lifetime.

^Yep This!!

Like in this thread - http://gamrconnect.vgchartz.com/thread.php?id=202595&page=1 theres only one guy/girl REALLY complaining about the DEMO ( just the DEMO ), while like 90% of the people on that thread basically dis agreed on him/her. 

I hope it does OK at least though (about 1 mill WW maybe more) so that it encourages Nintendo to take some chances and to really market new IP. It doesn't really do anyone any good if it doesn't go over well.

Unlike some games, Nintendo is really pushing this game. that been said, hard for me to imagine the game doing titanfall numbers (2.5m) but it doesnt need to reach that numbers to sell well.

Expectations are raised because Nintendo is spending a lot of money on its marketing campaign + it's a game in a very underrepresented genre on Wii U.