Intuitively, I would expect carbons 1/2 to have the highest electron density. MaxW's NMR spectrum does indeed suggest that 1/2 have the least density, then 3/6, with carbons 4/5 being the most electron-dense.
I suppose you could rationalize this conclusion by saying the the CH2 carbons (3/6, 4/5) will suck a bit of density from the attached hydrogens (because C is slightly more electronegative than H), whereas carbons 1/2 only have one H each to pull electron density from, therefore 1/2 have the least electron density. But my gut feels uncomfortable about this.
I attempted to calculate an electrostatic potential map of cyclohexene, but unfortunately I'm not proficient with the software. I think that's what we need here though.
For what's worth, here is a computer-generated model showing that there is more current density around the carbons you labeled 1/2: