Do aliens exist from the movie alien?

Well, I am pretty sure that this film was completely made up so no; the aliens from that movie are not real. Scientists are still trying to find out whether there could be life on other planets but it is looking pretty unlikely at the moment! The aliens in this film were made up of costumes and special effects.

However, it is narrow-minded to think that somewhere in the vast universe there isn't some form of sentient life. But then humans tend to be rather egotistical to think that we are the 'only' sentient beings in the universe.

Scientifically speaking, as it is a science question, it is not "narrow minded" to say no life is known to exist, until life is proven to exist. That's what "known" and "proven" are. No one here has denied the possibility of life; it has simply been acknowledged that it is not yet proven. That's not "egotistical", it is simply admitting a lack of certain knowledge. All science stems from acknowledging there are facts not yet known.