Does a martial art certificate have a value in college and university admissions?

It does not. However it could show that you r a disciplined individual who sticks to what he does. Meaning he won't quit the college after a short while. So getting admitted to college can become easier. A person who does not quit hard things. unless you look like a rough street fighter. cause so many many people who start a martial art class, just leave after a few months. cause they don't have the mental stamina. (Note: It takes 3 to 4 years to get a basic Black Belt. average of 3 nights a week going to class.)
Also If you love your martial arts, If you get a Black Belt or Black Sash or a higher "Dan", you will feel very proud of your self for achieving that. Nothing in life feels as good as achieving what you love. and of course many people you'd get to meet and befriend will show you a unique level of respect!.....like: ...yeah that's my buddy Tom (or Jane), He has a black belt in Hung Gar (or Shotokan), He is a nice guy with an edge!
Peace.
P.S. On a separate note, Many Martial Artists around the world have been trying to set up a 4 year college degree for all martial artists. however the problem with that is that there r thousands of different martial arts out there and many have 0 in common with each other. For example there r over 80 different styles of Karate, and about 200 different styles of Chinese Kung Fu. Some styles of Kung fu r as different as Wrestling vs Boxing, or a Ballet looking elegant style vs a Muay Thai looking style. then we have martial artists who only know of weapons such as the western sword or Japanese Katana(dozens of styles right there). such guys can royally kick butt if needed with just a long stick, a pool table stick can do them miracles! then you have hundreds of different wrestling systems from across the globe. and other things like the Hawaiian martial arts and something extremely unique like Capoeira. and then there is the issue of using the internal energy, in Kung fu it is called, The Chi. This is a very very controversial topic among martial artists. Cause only a hand full have it and it looks like magic, and then many others claim to have it but really they just make up fantastic stories. so because of all these, no one has yet been able to create a college system for all these groups.