To be fair, the "it's arcade so it's justified" argument isn't a valid one either. The Umbrella Chronicles, a Wii game from 2007, is an arcade-style game that lasts for around 8 to 10 hours and has plenty of replayability, unlockables, secrets and easter eggs.

Hmm I could have sworn I heard somone say something like that. Maybe I got you confused with someone else. Sorry :s

But I am interested in what you think about the game itself though. 

Yeah, I had it and I kind of like it. But, I said it before, SF:Zero, if we believe what Gamexplain said (they're really trustworthy so, yeah), has about 10 hours of new levels and paths. It's not just repeating the same levels over and over again, so even if you could do a main playthough in 3 hours, it has about 10 hours worth of new content, which is what really counts for me. The only difference is the structure of the game, which is not just linear levels, so it adds a bit of level exploring. 

SF0 seems to make up for it in terms of gameplay.

Umbrella Chronicles: https://www.youtube.com/watch?v=Ld6Laiz7SEE

Star Fox Zero: https://www.youtube.com/watch?v=htMRhXPzYhY&nohtml5=False

Judging from the demonstration displayed in a Japanese trailer, I don't think I'll have any trouble with the controls.

That's something left to see once we all get our hands on it and try it out. But why, exactly, does it seems that to you using a trailer?

Using a trailer? Considering the game has yet to release, what other way could I use to get a feel for Star Fox Zero's gameplay?

The question was meant for you to expand upon your initial comment. Umbrella Chronicles has different paths, unlockable missions, dual co-op, upgradeable weapons, secret archives and some other things. You linked both Umbrella and the Star Fox Zero gameplay, the later being a trailer. What, in the trailer, makes you think it will make up for the lesser total time?

From what I've gathered, Star Fox Zero also has differing paths, unlockable missions, dual co-op, and upgradeable weapons in addition to a variety of vehicles.

The greater freedom of movement for starters. Yes UC is a longer game but SF0 has a greater degree of freedom from what can be seen.

Fine about more vehicles, but the freedom of movement is still confined to the on-rails nature of it, right? In Umbrella Chronicles, you can move the camera around, but you're still locked  onto the on-rail movements. Boss battles (not all, just some) allow you to choose whether to cycle around it or go for direct confront, often moving around in different areas on the map.

Again, I don't mind an arcade game lasting three hours if it has good replay value. But, to be fair, it could really last much more. There's no reason it couldn't, especially not at that price.