Hi guys, I’m totally newbie … newbie in this forum and newbie in Blender 
I’m still in the learning curve of Blender (so many functionalities to learn !!!) One of my goal is to make “photo realistic” architecture scenes … This is my first post. Hope you will have many critiques to make it more photo realistic … Have a nice day.
One surefire way is to add some variation to the windows to make it look less “clean”. Also in my opinion the concrete texture looks off. The scale seems wrong and most modern buildings don’t have edges like that (or maybe it’s just your design).
Hi Profanity, thanks for your comment. I agree some variations on the windows are needed and I’ve to replace concrete by a metalic material. Having said that the scale and edges are more or less the same as the original building (photo attached) Have a nice day.
A number of things spring to mind immediately when looking at your two images. (By the way, having reference images that you refer to often is an excellent way of working. Well done!)
First, though, let me say that you are pretty close. Your lighting seems to be working as well. So you are just in the tweaking phase now.
Now on to the suggestions:
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Oddly enough, in your model the floating… I don’t know what to call them. The floating screens maybe? Anyway, the floating screens are too thick (in depth). Look at the photo and then look at your model where it angles away from you. Your model had given these screens some depth where the original does not have any. Looking closely at them, they look like they are made of metal. In your image they have a thickness that suggests they are concrete or something similar.
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In the original the space between the screens feels like it is a little bigger than in your model. Where the two halves of the screens come together above and below the actual windows should be further apart.
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If you look closely at the original, these screens have a lip on them on the leftmost and right most edges. These lips cast tiny shadows on their neighboring screens. In your scene the screens appear to be perfectly flat, They are also too far apart.
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This is hard to tell, but it looks a little like the top of your building is too short compared to the ref. But I could be completely wrong about that.
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In the original, there are thin metal borders around each window, something that I cannot see in your image.
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The edges of the building in your image appears to have a texture that does not match what is in the original. That said, whatever material you DO wind up using for the rounded corners of your building also appears to extend to the top on the original. I.e. it is a slightly different color than the material on the floating screens. It is slightly pinker and darker than the screen material. It also has some subtle reflections in it (you can see that in the form of a soft specular kick in the lower left corner of your original image). So make sure that this material extends across the top of your building as well.
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Your windows do not line up with the screens. I don’t know if you actually modeled the windows or if they are just painted in via transparency or clip maps, but they do not line up.
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Your concrete material around the windows is too saturated, too contrasty, and could use some cut lines in them.
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(and this is something I try to suggest for nearly every bit of non-character modeling I ever see), you should try to introduce just the tiniest bit of flaws to your model. Either via displacement, bump, normal maps, or directly in the model. Even though your original looks perfect (Is it a cg render as well?) in real life every single building will have some minor flaws to it. So you could subtly twist and turn each of your floating screens just the tiniest bit. This will cause them to catch light in different ways (again, just under the level of conscious perception) that will give your image some “life”. The same with your windows. Add a noise as bump to them so that when they reflect the sky they will seem to not be 100% flat. If you look at real windows, they are wavy and that shows up in reflections.
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Composition. Even if you nail these inconsistencies, the overall composition of your image is a bit bland and bizarre. The original has a very dramatic camera angle (more on that in a moment). If you want to use a more conventional camera angle (and I think that that is a perfectly fine thing to do), you should try to think more about your camera location. In your case, you have a magic floating cameraman. I.e. the “photo” clearly has been taken from at least five or six floors up (look at the perspective of the windows at the bottom of your image). But the clouds in the background are even lower without you ever seeing the horizon, which implies a fair bit of height (the five or six floors I referenced above). That is a weird location to see a building from. You would have to be in another building or helicopter to do that. But if that were the case, then you would almost certainly also capture some other buildings or greenery that are on the ground. (Unless you are looking at the very tops of some very tall buildings). In any event, take some time to look at real architectural photography and get a sense of where the camerawoman was standing, and what other kinds of elements show up in their photos that helps sell it (sometimes unconsciously) as being “real”. In the case of your original image, if it is real, then that angle was probably chosen so that they could frame the building itself without seeing its surroundings. And it may be the only angle they could do that from. If they had chosen a more conventional angle, you would have seen the surroundings.
Last, you might try either finding additional reference for you original building (that would be the best thing to do), or try to match the camera angle of the original photo so that you can look at your image side by side with the reference and see what, if any, differences pop up.
In the mean time, even though I had a lot of critiques, you are doing really well! Keep going and your already good image will pop out and look even better!
Also: I would suggest … “think about where you want to put your camera.” After deciding on the scale of your picture (i.e. “how many Blender Units correspond to how many real-world feet or meters?”), carefully lay out your set … using, initially, simple boxes for each one of the buildings. Add a sunlamp and a cloudy-sky backdrop, then start moving your camera around.
Each time you find a likely spot, duplicate that camera, leaving it right where it is and switching to the new camera as you continue “scouting for positions.” It is actually very important that you consider “the real world” when you choose where the camera should be, what lens (zoom or telephoto), and so forth.
Eventually, you’ll decide: “I think that these cameras are perfect.” (But, don’t delete the other ones. You never know.)
Many architectural photos are taken using “old-timey” bellows cameras, because the lens plane can be positioned independently of the film plane … the so-called Scheimpflug Principle, which is used to avoid “converging lines.” Fortunately, in Blender, you can (and, should …) use “Orthographic (vs. Perspective) Projection,” as fairly-well discussed in this WikiBooks article and elsewhere.
When you find the perfect place to put your camera, and just the right “people, cars, trees, and other trinkets” to put into the frame and exactly where they should be … even though, for the moment, those “trinkets” are nothing more than cubes, cylinders, and cones … then you’ll be ready to consider … lighting.
And then, when those cubes and cylinders and big-box (heh …) buildings are set in "an architectural photograph that Vanity Fair would be proud of … then you can start to model things, because then(!) you will be able to clearly see what actually matters to the still-photo or movie that you intend to finally make.
You see, until you know that … until you can see it … you can spend huge amounts of time doing things that simply don’t(!) matter.
As you work, make very aggressive use of “OpenGL Preview.” It produces very good imagery and it does it very, very fast.
Thanks so much for your full analysis !!! I will try to apply your recommendations as soon as I will have the time 
Very good for a first attempt! Better than I can do!