the game has different "paths", you arent replaying the same levels over and over again (with the exception of level 1).

Playing the campaign over and over again in Star Fox is not like replaying The Order or Uncharted. Those campaign stay the same even on harder difficulties (for UC, The Order doesn't have difficulty settings). 

In Star Fox, you replay the campaign to experience the levels you haven't played before. Here's the map for Star Fox 64:

The only things set during a playthrough is that you'll begin in Corneria and end at Venom. What you do in the levels determines where you'll go next. This means your first playthrough will most probably be the easy route, then you'll try for the middle road through Solar, then the hard road through Sector Y. You can also start in an easy route and warp to the harder route later. There's a lot of paths you can take making the experience different everytime.

Then there's also the challenge of getting medals in each level which bring another level of replayability to the game.

Complexity of the gameplay isn't dependent on the maneuvering alone. While the player in UC is restricted to the linear path set by the camera, he also needs to give some input regarding certain situations. Standard and fast zombies are required to be dispatched with a headshot, or your score won't increase. Certain furniture can be destroyed for more rewards (and in some - albeit isolated - cases, they open up to some bonus places), secret files which include story data and some other things are required for maximum stats, and taking choices when playing an specific part which leads to different places to visit, each one with their own zombies, furnitures and secret files to be found. This without taking into account that there are more enemies than mere zombies, which also include particular critical hit zones and other behaviour. The leech monster, for example, throws leeches at the screen, forcing you to choose between dispatching those leeches first (which cause minimal but uninterrupted damage) or go for the monster (which has a more erratic attack behaviour but deals much more damage).

I'm not arguing that moving around with a ship isn't harder than shooting on a static camera, that's for sure, but the gameplay can be as complex if tweaked well enough, which is the case in Umbrella Chronicles. Add to that the fact that only by getting A or S rank in certain story missions you'll unlock another story missions. There's eleven obligatory missions (that take around eight hours to complete), and then there's another eleven missions, each one with their own story cutscenes, dialogues and secrets to find. For one to play these secret eleven missions, he must achieve A or S rank on the eleven obligatory missions, which is no easy feat.

High replayability and maneuver might be StarFox plus, but there's simply no excuse to have a campaign that short when they could push it a bit further. And according to Gamexplain, it takes ten hours to unlock everything; it takes eight hours to simply beat the game in UC. There's the problem I have with SF's lenght.

Replaying Star Fox 64 didn't require me to think about replaying it. I wanted to replay it because it was enjoyable and when I scored higher at the end of a stage after learning enemy patterns and practicing tactics, it was fulfilling.

There's a whole genre of it: they're called shmups. Short campaigns but gameplay that makes one want to practice and perfect because they enjoy the challenge of mastering the game and its mechanics.

Oh FFS, i didnt go through reading everybody's comment to know exactly how SF game works.  Clearly the first person that replied to my text never corrected me when I was trying to understand this game in my first post (but I guess you didn't read every comment people posted as I haven't read every comment either). 

But you know, FFS since Star Fox only sold a few million means there are billions that still never played the game that don't know how a SF game works!!! xD 

I'm getting tired of people thinking that everybody should know everything about every game just cause we're on a gaming site.

FFS chill the F out.

The Order shouldn't be compared to games with replay value.

The Star Fox games also have similar aspects to them: a variety of enemies that can escape your shots if you're not quick enough thus reducing your score, certain parts of the map can be destroyed for bonus stuff, different enemies with various attack patterns, enemies that can block your shots, projectiles that have to be outmaneuvered or destroyed, etc. etc.

Okay, with a game like UC, what sort of tweaking are we talking about here? You'll have to explain because I've never played UC.

OP did not use the word "everything", OP states "every stage in the game + alternate paths (I guess ...)". I imagine perfecting your tactics and learning every stage's patterns, intricacies, enemies, etc. will take longer.

I don't expect people to read all the comments, or to know about SF games but I expect people to read the OP. That's why this thread is open, because someone did the work to start this. And, you know, the first lines of the OP are:

"- It took them 10 hours to unlock every stage in the game + alternate paths (I guess ...). 

- He says that you could go through 12 levels in one playthrough which is quite different from SF64 where you could go through 7 levels. He feels that the main missions are longer than multiple levels from SF64 too. Side missions are short tough but there's quite a few."

Which basically explains that every stage takes 10 hours, that there are alternate paths and side missions. Which pretty much explains all. And with reading the OP, you'd know how SF games work more or less. And it's the minimum requirement if you want to post in a thread that this person started, I think. But, well, to each his own I guess. Maybe it's a big assumption.

And leave the mocking at home. I didn't mock you and I won't do that. I've just stated that I'm tired that people are talking misinformed, and the aggravating factor is that it's stated briefly in the OP, so I don't really know why all those comments. We have criticisms of people saying that 10 hours is short for modern times, and I feel that's worth discussing, for example. We have comparions with UC which I think it's a pretty good comparison with another shoot'em up. But I don't really know where you exactly read that the game is repeating levels over and over again like you stated on your first post (yes, I've read it believe it or not).

Here's how I see it; based on prior entries in the series like the SNES and N64 games, I am going to get dozens if not hundreds of hours of playtime out of it.

So I'll actually be getting a lot more from it than most modern blockbusters, where I'll play the 4-8 hour campaign once and never touch the game again.

Come on, let's be realistic now.

Normally this would be pretty bad, but since this is Star For we are talking about (known for its replay value) I think everything is going to be fine.