Have you read through this Q&A? Quite a lot of us go through issues just like this. It's possible these uber-amazing people you're feeling inferior to are feeling the same way (possibly even about you). See also Q&A's on impostor syndrome, which it sounds like you might be experiencing.

One researches X because one wants to understand X. The satisfaction comes from making some progress and understanding. It is irrelevant that someone else is better, except to the extent that it conditions the professional circumstances in which one can study X. One focuses on doing something creative, and doing it well. Others can serve as models for how to do it well. Fortunately intellectual activity is not as well delineated as sprinting 100m, and there are many ways to progress without being the fastest. One does what one can according to one's standards and leaves the rest to others.

There is no comparison. Everybody has a different set of circumstances; better IQ, education, teachers, schools, money, backdoor or connections to places with resources, friends, etc. You are never competing under the same circumstances. Having said that, you can aspire to be someone; good motivational target. However, as everyone has a different set of circumstances, you will contribute in your own ways. As Magneto (from X-Men) said to Pyro, 'You are a god among insects. Never let anyone tell you different. '

Don't forget that a PhD is only a "training course" for research. If you stick at if for say 20 years, you are quite likely to become the "world's leading expert" in something - though it may not be anything that most researchers in the field either know or care about!

You are doing research. Chances are that even the brightest people will work on irrelevant stuff for years because research topics are pretty narrow in size. But that's not the point. Everyone brings certain experiences to his workplace, the best thing you can try to do is to either 1) put your skills to work or 2) dive into a new topic to get new skills. Either way you will most likely do something useful just along the way.

Calm down and relax. Not even Feynman, Einstein, or Susskind redraw the field in their PhDs. That happened after the PhD, for some years.

I realized a year or two ago that all in all, I'm a mediocre computer engineer. Average at best -- and I can say that because I've worked with some amazing computer engineers. But I also realized -- you can be sure I'll be the best dang mediocre computer engineer I can be. And that was the most liberating feeling in the world - because it means I only have to compare myself today against where I was yesterday. I can't say whether or not that'll be enough for you. But it's enough for me - and hence, I've come to terms with the fact that I'll never be among the best :)

@tonysdg I'm in a very similar place. As long as my boss is happy and I'm improving, then that's all I care about. I also realised something else: companies know that the average coder is mediocre. In general, employees aren't superstars. They're average. Me being mediocre is not going to get me fired unless I'm also lazy.

WRT the mid-rank college thing, there's more to life than which college you attend, and more reasons for choosing a college than its ranking. For instance, I chose where I wanted to live, which constrained my choice of college to the mid-rank state university that is located within commuting distance. That hasn't stopped me (or some of my classmates) from doing world-class work; it just means that when I'm not working, I can hike, bike, ski, ride my horse, and otherwise enjoy life :-)

You'll survive. I originally set my heart on becoming a movie star. Am I a movie star? No. Did I get over it? Yes. After a while it's like, so what?

What does "the best" mean to you? What do you think "the best" means to your advisor? To your other colleagues? To famous names in your field? I imagine any two people would define it quite differently. On a slightly different note, as Thomas Carlyle said: "Every [person] is my superior in that I may learn from [them]." And just as likely, by the time you are done with your PhD, people will be able to learn something about their own field from you. That makes you their superior! :) And if everyone can learn from you--you are superior to everyone--then aren't you the best?

It's not hard to be the best at what you do if you go niche/specialize enough. In the limit, the niche is being you. No-one can be better than you at being you. Similarly if you find some problem within CS that no-one else is working on, you can be the best at that.

Just having a bachelors degree in a field puts you ahead of the majority of the world. Earning a doctorate puts you in a very very small group, relatively speaking. Compared to the whole world, you're already among the best. It depends on your perspective.

I have an IQ that puts me in the top .4% of the population. I have friends in the triple-nine society, which requires being in the top .1% of the population. Oh dear, how can I live with myself?

Being a world-renowned expert probably sounds pretty cool, but it really doesn't give you any sense of completeness at all. If and when you achieve it, you won't care and it'll come to mean nothing to you. All that'll endure is whatever compelled you to go down this path in the first place.

Almost be definition, 99.99% of people won't be as good as the "best" person in a field (if such as thing exists)... 99% won't be as good as the top 1%... 90% won't be as good as the top 10% and so on. If you can start in the top 50%, you're already "better than average" and then aim to improve from there. But mainly, enjoy what you're doing.

Not being the best can be a great advantage, because you are in an environment where you can learn a lot from the others, and have the pleasure of learning it new.

For staying inside a field you don't need to be the best, you "just" need to be good enough. So the real question is if you are good enough? If you really want to be the best, you will fail with almost certainty and where is the sense in that.

Sometimes, being different from everyone else in your field is an advantage, because you may be able to make that connection with your experience that others would never have thought of. Just do the best you can, and don't worry about it.

I tell my girls, 4 and 6, that if they base their self worth on comparisons to other people, they're always going to be disappointed.

Compare your new self with new found insight and talent added .. progress that is much more satisfying..

Stay close to the best. Manage the best. Mentor the best. Identify and develop the next generation of the best. There is a sublime greatness in this, and a complete satisfaction.