I disagree, cycling is great.
I raced BMX when i was younger and my legs were very strong. In my late teens, i was squatting 250 for reps at a bodyweight of around 140, natural.
When i stopped cycling, my mass and strength went down.
Look at any professional cyclist and their legs are much more muscular than any bodybuilder, pound for pound.
A great way to pack on mass and strength is to do some hill sprints on a bike. Find a decent hill, about 60 degree incline and sprint up it on your bike from a stranding start for around 70m. Do it a few times.
What sort of bike do you have. Keep it on a low gear at all times......make your legs do all the work. I used to ride a BMX which had one gear.......my legs.