I'm sorry to be the party-pooper here, but that claim is extremely generalizing. Saying mars in capricorn gives a person the highest chances of success is like saying that sun in sagittarius gives you the most luck in career (and here is a list of all the celebrities born under sagittarius:
http://www.astrotheme.com/celebrities/sun/sagittarius/1.htm)
Incredible list, no? well, it should be, considering it pretty much gives the most popular celebrities from a data of about tens of thousands of people..... btw, from that list you gave, 5 out of the first 20 people were born in a year when mars spent about 6(!!!!) months in capricorn.... naturally, there IS a connection between the stubborn, consistent and hardy mars-in-cap, to the ability to battle obstacles in order to achieve success. But it is too generalizing. As I said, it's like saying that having a sun in X makes you this and that. As people who deal with astrology (whether as a hobby or profession), we should know that a person's traits and abilites are not solely based on their sun sign, NOR their mars sign.
After examining a few of the most noticeable celebrities of our era, specifically, female celebrities, I have come to a non-statistical conclusion. It is nothing I would consider scientifically proven or anything like that, but when I saw it, I immediately searched through several more charts.
And this is my conclusion: the majority of female celebrities have a triangular (meaning 2 sextiles and a trine) relationship between sun-mars-jupiter. It seems a lot have a sun sextile their mars, and a touch of jupiter usually comes in, or if jupiter doesn't aspect neither - it usually leads to squaring (or any aspect with) venus. For real. I think it even makes sense, because for a woman (or any person) to be successful, he or she needs the will/ego (sun), drive (mars) and a fair share of luck (jupiter) to go hand in hand. Venus usually adds in the beauty and femininity, and squaring with jupiter is craving the attention and the lights. But the triangle between sun-mars-jupiter or any combo among them, really seems to come up in many charts. Especially sun sextile mars. That is the most practical aspect, and it doesn't matter where the mars would be (miley cyrus as an example, has mars in cancer, and she's like a multi-millionaire, or penelope cruz, also with mars in cancer)
I started with Angelina Jolie, Rihanna, Megan Fox, Kristen Stewart and Miley Cyrus. They all have sun-mars connection, and most have jupiter aspecting sun/mars/venus. After that, I've checked about 2 dozen others, and they all seemed to fit in with my "theory"....
I also tried to see if this works with male celebrities, but I think they have other factors coming in for them.... I think a lot of the heavier planets (specifically uranus, neptune) influence them, but haven't had any luck in reaching concrete conclusion like the above (which, again, is not something I claim is a fool-proof theory)
And anyway, I think different areas of life demand different kinds of skills, as obviously movie stars' and musicians' success cannot be measured in the same way as that of a politician or a scientist. Of the latter, I'd probably expect a heavier influence of mercury by the heavier planets.