The earth has 149mil sq km of land area so those suburbs would take up about 1.7% of the land. If you subtract out antarctica (14 mil sq km), siberia (13 mil sq km) and 3/4 of canada (7 mil sq km), the sahara desert (9mil sq km)... you're still left with about 106 mil sq km so we're using about 1.8% of the land.
Density isn't evenly distributed you say? Well, let's look at only china then... Some 1.4 bil people in 9.6mil sq km. Everyone living on in 500 sq m lots means 350,000 sq km, or about 5% of the land. Lots of western china is too inhospitable you say? Fine, subtract out Xinjiang, Tibet, Inner Mongolia and Xining (forget the fact that 60mil+ people live there). That's half of china's land area! You're still left with around 4.860 mil sq km. So everyone's suburban lots would fit in about 7% of the land.
My point here is that the earth is not really as crowded as many people seem to believe. It only seems crowded if you spend the majority of your life in or near dense urban areas. Which most people do these days. So most see it that way. There are still vast tracts of nearly uninhabited land and even vaster expanses of sparsely inhabited land. Sure, these are typically not the really nice bits of the earth (from a human perspective), but we do have central heating and A/C now, right? :-)
