[Ditto]

Fair enough, but wouldnt an extremely thick atmosphere help to keep that heat in?

A 'thick' atmosphere also significantly reduces the amount of solar radiation reaching the surface. Even though it is much closer to the Sun than Earth, Venus recieves 40% less solar energy from the Sun.

[Vanders9]

Granted, but the fact that less energy reaches Venus from the sun wouldnt matter if, as you say, Venus is making so much of its own.