Who is the strongest Super Saiyan?

The strongest super Saiyan is Goku, in my opinion. His very first transformation into a Super Saiyan makes for him a pivotal point and a turning point for the entire Dragon Ball series as a whole. It was after his hair turned blonde thought that he was in for the duration with no turning back.

He got a massive boost of power when he fought Frieza on Namek. He gained the ability, and that is why he is the strongest. Had he not gained power, the answer might be quite different but...he did. That made everything turn around for him. Goku is the strongest, and I believe most would agree on that one.