From what we've seen of the Wraith so far, I don't think they could take Earth and hold it without bombing all our cities from space, killing billions, then defeating their purpose for going all that way in the first place. Even then, Earth would definately put up a fight.
We've seen that our little shoulder wielded rocket launchers can take out a dart. I see no reason why our fighter jets + f-302s plus all our surface to air stuff couldn't fend wave after wave of darts.
We've got plenty of nukes just sitting around for those pesky hive ships. (unless they have shields that we don't know about yet)
Guns are not a problem.
Many countries have large standing militaries.
The rebel Jaffa owe us a bit and are now probably in control of tons of ha'taks as well as the other Goa'uld ships.
I'm sure if the Wraith used the tactics seen in the Siege millions of humans would be captured or killed. But with each assault the Wraith would suffer large casualities as well.
What do you all think about this?
Would it really be worth the large losses for the Wraith?