If you want great legs you're going to have to do some hard graft too. You need to go for sports that work the circulation of the veins, tone the walls of your veins and tone the muscles in your calves. Regular exercise is the key (at least 30 minutes walking a day and at least 3 hours of sport or exercise a week). In adidtion, pick exercise that is especially good for your legs:
Good sports: Walking, running on soft ground and cycling tone your leg muscles and are great for circulation, as is dancing (flamenco, salsa, etc) which streamlines them really well. Swimming builds muscle mass gently and hones your muscles, while stretching and yoga are highly recommended.
Bad sports: Tennis and indoor racket sports, which involve lots of impact with the floor; violent sports with a risk of shocks and trauma (ski-ing, fighting/martial arts and team sports, for example).