I was thinking about this not that long ago, and here are my thoughts:

A lot of space in games comes from FMVs, generally games done by Nintendo don't utilise a lot of FMVs.  This is probably due to the N64 using cartridges and that might have set a precedent concerning how many FMVs are in 3d Nintendo games.

SSBBrawl came on a dual layer disc, MP Trilogy did and so will Other M.  The Last Story almost certainly will (Lost Odyssey came on 4 discs, if I remember correctly).  I'm pretty sure Zelda SS will as well, Zelda TP had a decent amount of FMVs considering it had to fit on a Gamecube mini disk, so I'm sure  Skyward Sword will have more and possibly orchastrated music or voice acting, all which will take up more space.  It could also possibly due to not many Nintendo games having extensive voice acting.

It's also worth noting that Nintendo have always made their games relatively small size wise, just think about how little games came on 2 GC discs, I can think of Tales of Symphonia, Resident Evil remake, 4 and zero, both Baten Kaitos, Zelda WW (one was a bonus disc though)  MGS Twin Snakes and that LotR RPG.  Even then, most were 3rd party and DVDs hold roughly 2x as much.

I'd like them to utilise the extra capacity of a dual-layer disc but only if they utilise it well. I read that Skyward Sword will feature a 'denser' but smaller overworld than Twilight Princess, so I'm not sure what that means for the overall size of the game. If they stick in fully orchestrated music and a heavily populated overworld it may very well be dual-layer, but it's not as if I'll be disappointed if they don't require that much capacity. Both Galaxy games fit on a single layer disc, and as far as I am concerned, they are two of the finest gaming experiences ever created, never mind this generation.

Mr.T-Tar pointed out The Last Story as a possible dual-layer game-if that's the case, we could have a truly epic RPG on our hands there. That's the kind of use of the extra capacity I want-if it benefits the game, use it, but don't try and force content into the game just for the sake of filling the disc.

only the best game ever made. New Super Mario Bros Wii. I'm fairly sure it is around 300-400 MB.

EDIT: also as my contribution to this thread, bigger is not always better. Sure, they could have put 200 levels in the game, but Nintendo wants you to have a sense of accomplishment with actually beating it. Most people probably give up before beating every level in NSMBWii, if they doubled the size I would bet only the hardest of the hardcore would actually bother to beat every level.

So what you're saying is they could have a wii: mario all-stars in the future?

Would you pay the extra 60 cents on top of 50 bucks for a dual layer disc cost over the regular DVD?

I certanly wouldn't...

$49.99 - sold!

$50.59 - no deal!

I dont think SS will take dual layers.Its possible but i dont think so.

TP fit in a Cube disc which had 1.5 gigs.One side of DVD with 4.7 gigs offers more than twice the space to work with for SS and probably will be used. last story is might include heavy cutscenes because its an RPG , and uses a powerful engine unlike TOS so yeah, that might be dual layer.

A smaller overworld? That kind of sucks also do you have a link possibly or remeber which site cause I'd like to read the article. I'm going to assume there not using a dual layer then if there going with a smaller overworld, even if it is denser.

I personally think they are taking a step back with that one because one of the enjoyment for die hard zelda fans ( well for me at least) is  looking forward to a larger overworld, which they seem to do with each new game.

oh is easy to fit more in a denser albeit smaller world. TP was large, but often it was vast spaces with not much going on, not animated creatures, just plain ground with a poor texture underneath, you could see the objectives in the distance but there was a lot of space with pretty much nothing. Filling everything properly at 3X textures means a lot of extra space. 

ROFL! I highly doubt they would charge the consumer the extra 60 cents.