I'm on my sixth SLR camera and I've had some fine and mediocre lenses. They all are from Nikon, Canon, Sigma and Panasonic and here's how I rate them for stills and video.
Nikon 18-70/3.5-5.6 G
This is a really fine lens. A bit slow but I've made some pretty nice pictures with it on a Nikon D70, D40x and D90.
A good focal length for video and decent in light performance but nothing you would use to shoot in dim scenes.
Nikon 24/2.8D
Nikon makes great lenses and this is no exception. I love the quality of the "D" class lenses. I love the feeling of the focus ring.
Somewhat soft wide open for stills but very nice to shoot video. I would consider this to be a very nice lens to establish a scen.
Nikon 35/2.0D
Same wonderful quality as the 24/2.8. The aperture of 2.0 makes this lens a very good video lens.
Nikon 50/1.4D
If you consider the price this is the best lens of all Nikon lenses imho. Excellent built quality.
It works from 1.4 and up with superb low light capabilities.
Nikon 85/1.8D
If you are considering a sharp lens this is among the sharpest lenses you can buy. It does not have any problems at all!
F1.8 makes it great in low light.
Canon 16-35/2.8 L USM
I really like the feeling of this lens. Very good built quality. Decent picture quality. A bit slow but there are no fast Canon zoom lenses.
The best use is to have it on a steadycam but other than that I prefer the other Canon lenses.
It's not bad but when you can get in the region of 1.2 to 2.0 I think 2.8 is slow.
Canon 35/1.4 L USM
This is almost as nice as the Nikon 50/1.4 but it's wider and that's great. If I had to choose one lens to use on the 7D this would be the lens.
Excellent in every situation. The "L" series lenses are so well built (well most of them are). Autofocus is fast and the focus ring is smooth as can be.
Canon 50/1.4 USM
If you consider the optical quality of this lens it's on par with Nikons 50/1.4. But the Nikon has a better built quality.
It's hard to beat the price/performance and for stills it works like charm but for video and manual focusing the ring is a bit to narrow.
Canon 50/1.2 L USM
If there's one lens that is on the extreme edge this is it. F1.2 is among the lowest F numbers you can get (Canon had a F0.95 lens).
For stills I prefer the Canon 35/1.4, it's a better lens really. But for video this lens is ok and it's easier to make smoother focus pulls than the Canon 50/1.4
The focus ring is still a bit narrow but much better than the one on the Canon 1.4.
Probably the Nikon 50/1.4 is a better lens but if I have to have a 50mm lens that works for stills and video this is still the best compromise on the 7D.
Canon 85/1.8 USM
Just as the Nikon 85/1.8 this a lens with few faults. I'd like to get my hands on a Canon 85/1.2 L. But it's just to expensive.
Sharpness is superb and although it's not an "L" lens it's quality is great.
Canon 100/2.8 L IS USM
If there's on "L" lens that is lacking in built quality this is it. It feels like cheap plastic on the barrel.
But it's really sharp and fast as long as you don't go from macro to infinity where it can lose it self.
IS is great and very useful for video. A bit slow at 2.8 but when you do go macro DOF is narrow thin.
Canon 135/2.0 L USM
This is also something really nice when you shoot video. It's fast at 2.0 and it gives you a better reach than the 85/1.8. Great broad focus ring and built quality.
As sharp as the 85/1.8 but a bit less light throughput.
Sigma 24-70/2.8 (non USM)
One of the standard zoom lenses along the 70-200. On full frame cameras the 24-70 and 70-200 covers a wide spectrum and could be a perfect duo
I had the non USM version of this lens.
I don't like lenses that expands and with this lens it's even worse since it expands when going wider rather than most lenses that expands when going tele.
The lens will obscure the flash and since it's expanded at it widest it's really bad.
Built quality is okay but I never could get a consistent result with this one. It's soft wide open so you really have to stop down in order to have some useful sharpness.
DOF is shallow. I much more prefer the Canon 24-70/2.8 L lens which is sharp wide open.
Sigma 28-300/3.5-6.3
A bad and slow lens. Stiff zoom ring and just boring.
Sigma 30/1.4
This lens is fast and has a very sweet focal length. It's sharp in the centre but falls into blur at the edges.
Ok built quality but I like both the Nikon 35/2.0 and especially the Canon 35/1.4 much better.
Sigma 150/2.8 Macro
Of all Sigma lenses I had this is the best! It's sharp, it's picture quality is very good.
It works great for macros and it's a great tele lens. Very nice plastic housing.
Sigma 70-200/2.8 Makro
This is one of the standard lenses when it comes to focal length one would have. It has a buttery bokeh and feels very nice to handle.
It might not be super sharp but ok. It's on the heavy side so many times I prefer the Sigma 150/2.8 because it's lighter and better.
Great for close ups with nice smooth shallow DOF.
Panasonic 14-140/4-5.6
This lens is for the GH1 and it's a very good match for this camera. It got OIS, it's very sharp and makes the GH1 almost as user friendly as an ordinary camcorder.
It's not so great for low light scenes or indoor stills and I don't like to pull focus manually with it.
Panasonic 20/1.7
It's small, it's light, it makes the GH1 feel like a toy. But don't be fooled the images you can get from this one is amazing.
It makes the GH1 shine and works for stills and video. But the focus ring is to narrow, it has the focus by wire thing so to
pull any sort of manual focus is difficult to say the least. I would consider this a must on the GH1 since it makes such beautiful imagery.
So If I had to only choose three lenses?The 20/1.7 on the GH1 is easy. The Canon 35/1.4 L USM on the 7D is also easy.
As for the third lens I would probably go for the Nikon 85/1.8 or the Canon 85/1.8.
But I want to get my hands on that Canon 85/1.2!!!