Of course the possibility exists. In fact, estimates go as high as a BILLION Earth-like planets, just in our galaxy. The bigger questions are how many of them are reachable in any real scenario, and how many are capable of supporting life. There are two real reasons for asking this type of question. One is whether there are planets that we could colonize. The other is whether life has already developed on other planets, especially any form of intelligent life. The distances involved between Earth and the other planets play a part in any meaningful answer to either. Do the distances involved make travel impossible? And for any contact with other intelligent life forms, not just the distance, but the age of the universe plays a part. There has, after all, been intelligent life on Earth for a very, very small percentage of the age of the universe. Perhaps many intelligent species have already come and gone elsewhere in the universe, or perhaps they will develop in millions of years--at which point, humans could well be extinct. I guess we will just have to wait and see!
The assumption is that with so many stars and planets in just our own galaxy, let alone the entire universe, that it is likely that there are situations where a planet is in the right spot relative to a star: a spot where life is possible. There are 200-300 billion stars in the Milky Way and hundreds of millions, or maybe even billions of planets in this galaxy. Considering the enormous number of stars and planets, (solar systems) and that these systems would likely evolve in similar ways to our own, it is possible that a system would evolve where a planet would occupy the habitable zone: a region close enough to the sun to sustain life, water, etc.
There have been optimistic theories like the Drake formula which supposes that, based on solar system formation, there are probably a million extraterrestrial civilizations in the Milky Way (I've also read it comes to 10,000 planets). However, knowing the complexities of DNA and the specific, biological and evolutionary conditions of life, the odds of other civilizations could be next to nothing. Compare Drake's formula to Andrew Watson's theory (3rd link) that it is highly unlikely.
Italian physicist Enrico Fermi asked the question, "If there is extraterrestrial intelligence, why haven't they contacted us?" One answer is that inter-stellar travel takes too long. Another is that there aren't any aliens to visit us in the first place. I guess your conclusion, if its based on science, would depend upon how rigorously you define the conditions for life and how possible you think it is for those conditions to be met considering the known evolution of solar systems.
Yes, there are distinct possibilities of other planets like Earth in the universe. But, my knowledge of this is based on Christian religious beliefs and might prove controversial to some.
Without providing the link, I will simply say that God said to Moses: "And worlds without number have I created; and I also created them for mine own purpose."
I don't know what religious beliefs you have or even if you believe in God, but I do and that's what I believe.
Yes they are called pandora to read about I wish you could follow the provided link but Avatar blew up google whenever you search pandora gRRRRRRRR... I will give a little bit though: Pandora is a place close to a star like our sun and is just the right spot it dosen't have to have a moon unless you are also looking for eclipeses and even with a moon it would have to be just perfect so there is a 1 in 1,000,000 chance there is a pandora right now... The universe is still expanding from the big bang though so evently there might be one and if we find it then We will know but as of now we can hardly get a UMS or Un-maned spaceship out to pluto to take pitures (Even though it is a Drawf Planet) The next atchivement is going to be to land on mars, then leave the solar system in a UMS, and so on one thing I whould like to see in my life time is escapeing jupitars gravity and it's escape velosity is something close to 37 miles per sec. Pandora probley exist though(Minus the Na'vi).