There's no place to list "I'm a nice kid" on a college application. But that doesn't mean that nice kids don't get a lot of benefits.
Nice kids get extra help from teachers and counselors when they ask for it. They get more effusive letters of recommendation. They'll make a better impression on college interviewers and have a better chance of being taken off wait lists. They're more likely to have people in their corners, ready to work and lobby and fight on their behalf. They've earned those benefits by just being good to other people.
Being nice is free and easy. It puts you in line for karma points. And I have never once seen a nice kid who worked hard end up without colleges to choose from. You might not be able to list it on a college application, but don't underestimate the power of just being a nice kid.