THAT would be really interesting, if it turns out that not only is there life all throughout the universe, but that it shares the same genetic building blocks.
I think more likely, it's simply a matter of what's "simplest" or able to happen with the resources available. The universe is a set age. As we understand the basic building blocks of matter, there are certain rules everything is governed by.
It's the same thing, that people in certain environments will act certain ways. Other 'types' of lifeforms are surely possible (surely?) but they're likely more 'difficult' and not the first type of species that would develop.
That's a bold assertion, given how little we know about the universe. Perhaps Earth is the outlier, and most other life in the universe is made of different building blocks. We simply have no way of knowing. But given how many factors are involved, it seems reasonable to expect that life which evolved under different conditions would be, well, different.
On the other hand, maybe all life in the universe was "seeded" by a group of primordial aliens. Maybe there are humans or human-like beings, the only difference being slight variations around the eyebrows and nose, on lots of planets, just like in the Star Trek universe. 
Where we are discussing Life and the Universe, it's aragnot to claim even a fractional knowledge.
And to get off my high-horse, I'll give you your point, however we have to operate on what we do know, and some fair assumptions about how the rest of the universe works.
If the building blocks you're talking about are that we're carbon based life-forms, I'll give you that. However when I spoke about building blocks, I was referring to the building blocks of any kind of mass. Electrons, Protons, and Neutrons. However the (vastly) larger thing is designed and what elements it is compromised of, as we understand now, we can assume it's made up of atoms with those very same building blocks.
In the big bang, I believe there was a majority of Hyrdogen (or even single neutrons, with no electrons attached. A 'mass' or 'soup' of material as it is in a supercharged state) (please forgive my off hand, grossness with how I'm describing this. Please correct me/we can look into describing this better if we'd like). As things spread out (the bang) you have clusters that would form, and as things cooled down the forces that keep things together could overcome that vast engergy in that initial 'soup' at the center, and you have regular Hydrogen forming (making up the majority of most stars, to my knowledge) and as things continually progressed more and more shit from those same building blocks came together to make a billion different things (carbon based lifeforms on a rock for example).
Is that how Star Trek explains things? That's interesting. "Creation".
