Good question Alyssa, at BodyRock we say that it really depends on how you want to look! Basically cardio will make you skinny, but it won't help with body sculpting per se. Weight training alone will build muscle, but you need to do a bit of cardio to keep any extra bit of fat from hiding them.
HIIT combines cardio and weight training so you don't NEED the run, but I used to be a runner and I know that the long run is really relaxing and important as well!
So, if you want shapely legs for example, cut your runs to once a week or cut them out altogether. If you want skinny legs, keep your runs at 2-3 times a week and do HIIT twice a week.
Remember that HIIT will help you lose weight 9 times faster than cardio, but again, you will simply have a different body shape than a runner. After finding HIIT I fell in love with the combination of lifting and cardio. You can just get that "impressive" look so much faster and keep it with more ease.
Of course, the No 1 way of revealing muscle and losing fat is by eliminating fat-producing foods from your diet, ie. eating clean. We have a whole ebook about that: http://go.bodyrock.tv/qio0