It seems like this debate has gone as far as it can go, so I will just make this last point.
Modern day telescopes can see billions of light years away, and by consequence, billions of years into the past. Nowhere, in all that space and time, have we ever found anything to suggest that the laws of physics are not universal. If matter attracts matter in one part of the universe, then the same is the case in the rest of the universe. I will grant, it is possible we simply haven't been looking hard enough, but it seems fantastically improbable that the universe would choose to behave differently in our little corner of the universe. If our planet is an exception to this rule, then it is the only exception we have ever found, and we've been looking for a long time.
Thus, we see that everything in the natural world, from the formation of planets to the composition of dinner plates, can be described according to certain laws which to the best of our knowledge, do not seem to change based on time or location. And those laws, coupled with direct observation of other celestial bodies (The Moon, the Sun, other planets, and recently; extra-solar planets) tell us that large bodies like the Earth form spheres, not plates.