He doesn't have an argument because he assumes all games are made alike which is NOT the case.
Here's the reasoning and justification for the 3D slider on this game
If you've played a game called Echo Chrome on the PS3, you understand that the concept of said game is that angles and perception can be manipulated within a 3D space. To clearly navigate your way through that game and it's 3D space, you have to manipulate the camera to get a fix on the visuals and understand where pieces stand in context to one another. Without manipulating the camera, you have no idea where you are going. Contrast this with Mario 64, game x,y, and z.
Now, Mario 3D Land is designed with this very same concept! Except here, instead of having a camera to manipulate, which you have in past 3D platofrmers, you have a 3D slider to help you understand the depth. So that is the key difference. It was explained very clearly by Nintendo and Iwata. This game was designed so that you use the 3D to understand your area, and not a camera.
I don't even know if you're being serious here. There's like what, five rooms in the game that are comparable to Echo Chrome?
I totally agree with you, those five rooms are easier to navigate with the 3D on. With it off, it probably would have taken me a whole few seconds to "get" the optical illusion. Which is totally possible, as you've pointed out yourself navigating optical illusions was the whole game in Echo Chrome. Humans are capable of understanding 3D space on a 2D screen, very easily.
But yeah, I really don't even get what you're saying here. There's a 3D slider "to help you understand the depth"? Yeah, you know, even with it off I'm somehow very able to tell where things are in relation to Mario.
Is there anyway to tell which levels you beat with Luigi?
After you beat the last level M and L icons should pop up next to the gold flags on the level select screen to indicate who you've beaten a level with.
Edit: I haven't read this thread in awhile, hadn't realized this won a VGA, though it isn't really surprising. What else was even nominated for best handheld game?
It'd be cool if they do away with the handheld category at some point. I lot of people in this thread have said 3D Land is one of their favorite games of the year, and I agree. It would have been really cool if it had been in the running for game of the year without the handheld stipulation.
Doubt it would have won with Skyrim, Batman, Uncharted, etc. out, but handheld games are starting to look and play a lot more like console games. Not necessarily exactly the same, as obviously 3D Land's levels are much more handheld-suited than Galaxy's for example, but as budgets for handheld games increase I think they'll start to stand toe to toe with console games.