The article you linked to describes the angle of plane of the orbit - the circle it makes around the sun. These vary by only a small amount.

The axial tilt is different. It is basically how far the axis through the poles of a planet is tilted compared to the plane of its orbit. This is what you were thinking of initially - it can very a lot.

I think you were confusing orbital inclination with axial tilt. http://en.wikipedia.org/wiki/Axial_tilt