Here's a typical leg day routine for me. I'll warm up with leg extensions, 3 sets at about 75% intensity which is 160 lbs. Then I'll go barbell back squat. 6 sets, 15, 15, 12, 8, 8, 4. Leg press, same rep scheme but back up to 15 again. Leg extension superset, which is where I start to feel the most intense burn. Barbell back lunge, 3 sets 10 reps. Hamstring curl superset. And then I will goblet squat with light weight to failure. End with a weighted wall sit. If you get thru this torture you will build some nice looking legs in no time.
If you're looking to increase the size of your quads then you need to push harder. High reps with low weight is great for strength and endurance, but if you want more size then you should increase your weight to reduce your reps. 3-5 reps at a much higher weight will be just as difficult if not more, and as a result you will (with enough water and protein for recovery) increase the muslce size.
You may not be able to add enough weight to the leg extension machine to get you down to 3-5 reps. Barbell squats and the leg press machine are good alternatives. The barbell squats are your best bet because doing them correctly involves several muscle groups in addition to your quads. I could go on and on about the benefits of compound lifts, but that's for another topic.
So add more weight; do 3-5 reps; 3-5 sets. Good luck!