Nobody cares if you're "well-rounded". It's a gimmick that's been used for generations [1] to preserve the ethnic / cultural make-up of various groups. A simple way to verify this is by noticing that not all extracurriculars are created equal. With e.g. sports, you'd have to go to East Asia to find a place where, say, badminton and tennis are equally highly regarded. And good luck equating leadership in a WoW guild of hundreds of people with captainship of the local lacrosse team.

[1] At least since early 20th century Ivy League admissions got switched to the "interview / recommendations / extracurriculars" process in order to keep out Jewish applicants http://www.amazon.com/review/R2CVQUI4C0VDUQ/ref=cm_cr_pr_per...