How do we find a planet around another star?
Well, generally be seeing the motion of the star, demonstrating a wobble, and then figuring out what the missing mass must be doing.
So we can only see planets that wobble their stars. Which means that we would have no way to "see" the types of planets that are in our own solar system. In fact the kind of planets we can spot are big ones in close to their stars. The kinds of planets we know about, not surprisingly, therefore are all big ones in close to their stars.
We will have to wait until we can see smaller planets to find out what the balance between different kinds of solar systems really is.
As for other intelligent life, I believe the odds we will see it are low. Why? Because we don't see them. This is known as the Fermi Paradox.
Look at ourselves. Failing our wiping ourselves out, we are not that far from developing Von Neumann machines (ie machines that can replicate themselves). Once we have that, it is a question of time until we start colonizing the planets with our machines. In the relatively near future (say 1000 years) we are likely to set off for nearby planets. Within 50,000 years (probably a lot less) that effort is likely to achieve 0.1% of the speed of light. At that rate, we will finish covering the galaxy in 10 million years.
10 million years is an eyeblink on a galactic scale. So it seems probable that 10 million years ago there were no technological civilizations in the Galaxy, else they would be here. In 10 million years we will be there. The odds appear low that we will encounter any other examples.
So which is the roadblock? Life? Intelligence? Technology?
No idea. But I think that if we do find ET, it won't be in this galaxy.
Cheers,
Ben