Well you should be outnumbered by Aliens at least nearly 2 to 1, at least for everything bigger then a large Scout, but even those have a crew up to 16 on Superhuman difficulty.
Isn't the idea in XCom that at the beginning, you are the underperforming, underarmed primitive species battling genetically modified, more advanced aliens that are way better than you and your only hope is that you have more manpower than them (since it is our planet and you can draft from all armies in the world; whereas they have to ship their soldiers across the stars or grow them in vats locally)?
That changes after you catch up tech-wise, of course, but I think the beginning was intended to be like that, with the end more equal where you take on even stronger aliens but are much stronger yourself, and the numbers sort of even out.
If the aliens always outnumber you, outgun you because they are more advanced, and outstat you because you're a mere human to their gene-enhanced soldiers, what's left? I guess you have tactics, but that's a tricky thing to rely on in a game against an AI that doesn't really fight as a team. And hoping your soldiers stay alive so they become so much better after a while, but then that takes away the "gene-bred monster" feel.
Not saying it's not an interesting twist, but it seemed to me like a departure from the original philosophy.