In the Vulcans, Gene Roddenberry created an alien species that is both very relatable to Humans and also very different from us. There are Humans who pride themselves on living very stoic and spartan lives and there are Humans who rely more on logic than on emotions to guide their decision making but, for the most part, those ideas are a bit foreign to us. Roddenberry was smart enough to create the logical Mr. Spock and the emotional Dr. McCoy to act almost as a devil and angel sitting on Captain Kirk's shoulders. Kirk, Roddenberry's ideal future Human, was then able to display a balance of logic and emotion. He relied in equal parts on the advice of both of his friends but he had the innate intelligence to take only the best of both worlds into himself.
The genius of Spock as a character is that Roddenberry gave him a constant internal conflict. Spock is both Human and Vulcan and trying to live as a pure Vulcan. No matter what situation he finds himself in he is beset with turmoil from the inside. This gave Leonard Nimoy an amazing opportunity to create a very layered and nuanced performance. Nimoy's genius was that he recognized this internal conflict. He wouldn't just play an emotionless man but a man who was incredibly emotional and struggling to keep those emotions buried.
We have been fortunate to have almost 50 years of Star Trek for Spock to develop within. Throughout the original series in episodes like "The Galileo Seven" and "The Naked Time" Spock struggles with finding the balance between logic and emotion that Kirk is fortunate enough to have from the beginning. This struggle comes to a very satisfying climax in Star Trek VI: The Undiscovered Country when Spock tells Valeris that "logic is the beginning of wisdom, not the end." He implores her to also have faith (a very Human concept) that the universe will unfold as it should. Though still the "Ultimate Vulcan" Spock has now managed to embrace an important part of his Humanity.
Moreover, the design of the Vulcans was so simple and yet so compelling! The gracefully upswept eyebrows both complement the gently pointed ears and draw attention to the helmet-like hairstyle that is the pinnacle of simplicity. Many writers have explored the combination of intelligence and physicality that makes Vulcans (and Spock in particular) sexy. My favourite such piece is the TV Guide essay "Mr. Spock is Dreamy" by Isaac Asimov.
As Star Trek has evolved over the decades we have learned that Vulcans were once more emotionally-heated than even 20th century Humans! They were bloodthirsty and once warred against each other so fiercely that they seriously damaged their planet and came close to self-annihilation. A man called Surak developed a series of teachings and a way of life that preferred logic over emotion. He taught his people how to suppress their emotions and, in this way, saved the species.
The Vulcan concept of IDIC has become central to my personal life philosophy. Gene Roddenberry once said:
“If man is to survive, he will have learned to take a delight in the essential differences
between men and between cultures. He will learn that differences in ideas
and attitudes are a delight, part of life's exciting variety, not something to fear.”
To me, this seems incredibly...well, logical. Biologically, when two persons who are different breed a third, that third is stronger for having the biological diversity of two parents. The same principle applies culturally, intellectually and politically. When people who have different ideas about a single problem or subject are able to come together and debate they will usually find their discussion leading to the strongest alternative or solution. Anything that encourages critical thought and self-examination can only lead to improvements. Remembering always to respect Infinite Diversity in Infinite Combinations makes a great deal of sense. If we were a culture in which no one had an independent thought or ever questioned the way something was done we would stagnate. The Borg, anyone?
If all of the above isn't enough for you, Vulcans also have super-strength, they're telepathic and their culture has inspired great sci-fi stories like "Amok Time." Even those who have never seen an episode of Star Trek can immediately identify an image of Spock. They know he's a Vulcan and that he's "emotionless." That kind of pervasive cultural icon doesn't show up very often and it will live long and prosper long after anyone reading this is gone.