I've got all three of those cameras. I started with the 60D, then the 5Dmk2 and because niether one of those seemed to be able to pull off everything i needed, I bought the 7D.
you've said you plan on doing low light and landscapes. Most people will point you at the 5Dmkii, and while they arn't wrong, those are definitely that camera's strengths, I just can't bring myself to recomend it.
the 60D has the better ISO of the 7D and 60D, contrary to popular belief. But its nothing compared to the 5Dmkii. The big problem with the 5D is the AF. The 5D auto focus problem has been beaten to death, but the fact that its been such a hot topic should at least prove that it is a valid problem. The fact is that the AF on the 5Dmkii is perfectly ok for portraits and landscapes. Both "static" images. If you use the 5D for anything that actually moves, or has a shallower depth of field than 2.8 your going to be hit or miss on sharp images. Miss more than hit really.
Its been my experience that in anything other than very/extreme low light the image quality difference between the 5, 7 and 60D is negligible. Obviously you'll be able to "blow up" the images of the 5dmkii more, but any of the three will make an image @ 13x19 with no problem at all, which is more than most people need already.
When you look at those three cameras and instead of looking at what they can do, I think its important to look at what they CANNOT do.
I'd say that the 60D and even less so the 7D can't shoot handheld in very low light, without flash, without pushing the ISO into some pretty iffy levels. Depending on the use of the image, I would say that ISO 640 is the limit. Obviously others will disagree, and I've talked to wedding photographers that claim to comfortably use 1600 ISO shooting weddings with them, so your mileage may vary.
The 5Dmkii is obviously the most capable camera to shoot handheld in low light, but that doesnt mean it does it well. The AF system works poorly in low light, though it doesnt have any more difficulty than normal until very low light. Unless the target is moving, at which point the AF system becomes a little hit and miss. Again, more miss than hit.
The 5Dmkii cannot shoot moving targets. I'm sure there will be a bazillion people here that will decry that statement, for those, go grab a 7D (or a 60D even) and see what it really means to be able to shoot a moving target. Its well known that the 5D was never meant to shoot action, but they could have done a lot better than the bare minimum.
The 7D can do pretty much everything "well" but excels at AF and speed. The ISO performance is the worst of the 3, but not game stopping bad, even at 1600. Yes, I know I said 640 was the limit, but that is the limit "I" impose on the camera for production quality images. You could use 1600 pretty comfortably for home and frivolous images, as long as you use noise reduction software in your post workflow.
The 60D is pretty much middle ground between the two. For video and tripod work, this is my go to camera. The articulating screen is LOVE. the ISO performance is better than the 7D and worse than the 5D. The AF system is much much better than the 5D, but nothing compared to the 7D. The frame rate is much better than the 5Dmkii, but much worse than the 7D. There is nothing the 60D can really do that the 7D can't do a lot better really. Even the difference in ISO is negligible once noise reduction software is used.
Of the 3, if I could only have 1, the 7D would be the hands down winner. I shoot a variety of subjects including portrait and landscape and I find the 7D can handle it all. I do use the 5D for portraiture and landscapes, mostly because it does do a better job, but I wouldnt really miss it if it was gone.
The 5D mkiii is rumered to be around the corner, I would advise you to get the 7D and later, when the new 5D comes out, see if it isn't more your style.
Canon camera, Canon lenses.