Each of these 3 cameras bring something different to the table i own 2 7ds 1 5dmk2 1Dmk4 and i owned a 1Ds Mk3 and i still own a 5d mk1. I have sold images from all of these cameras so and they have been published and take it from me they are all good. For me The 7d can beat the other cameras in a few areas.

Im now waiting for screams from some other owners of 1D range. For 1 menu set up of certain things how you access live view and the video spring to mind for one. Another thing is suppose like me you are photographing wildlife with the 7d with the 600mm fited you have an equivelant view of 960mm at f4 the 1D offers 780mm at F4 to get nearer in image size you fit the 1.4 to the 1D that now gives you 1092mm at f5.6 now to get the shutter speed back the same you up the iso one stop now compare images there is nothing in it. Some may argue to crop in the people who use my work require a digital raw file size of 12MB
The 5d is better in image quality but if you can't track it you can't photograph it don't get me wrong the AF isn't bad on the 5D but it is'nt a patch on the 7D and the 7D is a tad behind the 1d mk4 for AF though it is better than some of 1D mk3's you get good and bad bodies with this model
Another thing i like about the 7d is i can use my 300mm f4 for handheld flight photography this is a very light combination when i use the 1d Mk4 i normally use the 300mm f2.8 with the 1.4 extender this is a lot heavier.
To me the best of the bunch on image quality is the 1D Mk4 just and i mean just you are pixel peeping.
The best for sport and nature the 1D mk4
The best for landscape work and weddings the 5d my 17mm lens is a
17mm field of view
The best for jack of all trades master of none is the 7D it's cheaper than the others and brings a lot to the table.

You pays your money and takes your choice there is no easy answer
You could print a image at A3 from all these cameras stand 4 feet away and you could'nt tell which camera had taken which image i tried this test on a group of photographers not long ago i also threw in a image taken with a D60 and i don't mean the 60D i mean the old one and no one picked that one out either.
Regards
Richard
Please feel free to contact me if you ever want to try the above cameras against one another