Well, this looks close to the scale difference between the minifigs and those giant people heads that used regular bricks for the body... :P
Hm. What a strange ad. I wonder what they're trying to say. There's an implication there that it's only boys who have imagination but on the other hand, they both built elephants. The girl will probably have the rest of the day to play while the boy probably took a week to build that elephant. I can't quite get a handle on this commercial.

That's a damn cool elephant, though.
I assumed that the girl didn't make hers--it's just some crappy store bought toy which inspires absolutely no imagination. As opposed to Legos which will let you spend hundreds of thousands of [your currency] to build one big ass elephant.
The little girl appears dissatisfied with her elephant. But that is all you get buying one box of Leggos. The boy embezzled from his father's company and bought a never-ending supply of Leggos which he assembled into the giant elephant in his back yard. This got him a free scholarship in a design school and he is now a leading architect. His dad was fired in disgrace and is now doing time.

How thoughtful of Leggos.
He's standing on her head.
She looks so... so downtrodden! There's something weirdly old-school Soviet worker poster art about this thing.

I think all of you people have the crazy.

The ad is showing that you can build something big OR you can build something small. He built the big one in the background, she the small one in the foreground - probably because the photographer knew that little girls are generally considered cuter than little boys. Thus, she got the little, foreground elephant.

She's not downtrodden (she looks quite happy to me), there's no subtext, and to the best of my impression no one is trying to do anything in it except appeal to the child like idea that building things out of your imagination is fun.

The sad part is they started at the same time.
I'm reading this ad as saying, if you want to build something really awesome, buy tons and tons of Legos. Or else you'll just be stuck with a crappy little elephant.