I’m no expert, I’m not going to pretend my answer is based on anything, just what I think is logical based on a lifelong interest in science and astronomy.
Life on earth comes in many, many forms besides humans. I believe there is definitely life out there, the universe is so incredibly vast that I’d expect that just about anything that can exist based on the laws of science (which we don’t fully understand yet) probably does somewhere, just the law of averages, and in fact it seems very likely to me that any form of life that has evolved on any planet probably has evolved in a similar fashion on at least one, and probably multiple other planets.
My belief is that the universe is so incredibly vast, probably not exactly “infinite”, but if not, there is probably something beyond what we think of as the universe…infinity does exist and something has to fill it, that’s the way I conceptualize it anyway, and of course I could be wrong.
Anyway, there are certainly billions and probably trillions of planets (or more) that could support life…I base this simply on the vastness of the universe and the concept of “infinity”. Life is tenacious, where life can exist, I suspect it most likely will take hold at some point. But the vastness of the universe and the laws of physics (at least to the extent to which we currently understand them), make it, shall we say, at minimum a very “advanced” proposition to traverse the distances between any two planets with “intelligent” life on them. Because of this, I’d say a society advanced enough to figure out a practical way to visit our planet (which is the only way any of us would be likely to encounter intelligent life on another planet in our lifetimes) would need to possess certain characteristics we’d associate with intelligent life on our planet.
What I mean is, if you look at the vast number of life forms we have on our planet, there are many characteristics that seem nearly universal, and when you look at more “advanced” forms of life, those who possess characteristics we perceive as “intelligent”, all such creatures including man share even more characteristics than we do with all these other life forms. Consider that there are insects with eyes and ears, but we don’t see them as nearly as similar to us as we do apes.
So, where does this leave me? My thoughts are that if on one planet, so many forms of life, millions of them just on this one planet, can have such variation, the vastness of the universe means that there are likely millions, maybe billions of intelligent species that have a number of things in common with man, but there are probably trillions to a factor of trillions of life forms that bear little or no resemblance to man, and surely an unimaginably vast number of these life forms have evolved to the point where we’d consider them to be intelligent. Of the pool of all intelligent life forms, that fall within a spectrum of no resemblance to man to almost identical to man, some random number may have evolved to the point where they could have mastered interstellar travel. Some even smaller subset of that might have figured out how to get as far as Earth…when you keep filtering into smaller and smaller subsets, that pool of potential visitors to Earth gets dwindled down to the point where it’s unlikely we will be or have been visited by intelligent life.
Any willing to try would certainly want to be aware of our capabilities and our limitations, they would want to observe us to learn how to approach us (assuming their intentions were to make peaceful contact with us…not a foregone conclusion…in fact a very large subset of those able to visit us might have malevolent intent). Based on all this, I would conclude:
1) We are very unlikely to encounter “intelligent” life in any of our lifetimes.
2) If we do, it’s a crap shoot to know if we’ll ever even get to see them before they annihilate us.
3) On the off chance that we are visited by intelligent life who reveal themselves to us in order to communicate with us, there will probably be at least “some” recognizable features, but given the vast diversity of life, the law of averages says there will be far more unrecognizable features.
So my conclusion is this….what might visit us at first would probably bear at least “some” resemblance to human life, and “some” to other forms of life on our planet. If we were to get to see the full spectrum of life on their home planet somehow, I’d say we’d find even more similarities. But in the end, I think what we’d end up seeing is something that would be shockingly different than what we know of life. So the answer is yes and no, and it will depend greatly on your perspective…but I’d say the layman’s conclusion would be “no”, but the scientists conclusion would probably be “yes”.