Unfortunately this is not an easy question to answer. Not because the answer is elusive, rather because it is varied. The posterior chain that is involved in walking and standing will be stronger in an obese individual by nature of having to haul the extra weight. Bone density is also increased for the same reason. As long as vitamin D & calcium intake percentage was commensurate with caloric intake, the femur, tibia, and fibula will be denser (hence stronger) than in a average weighted person of the same activity level.
The problem is that many of us that were obese for a long period of time either developed or already had injuries/ailments. Mine was a bad back, hips, knees, and ankles from a car accident. While the muscle and bone is fine for the most part, the joints were a mess. For people like me, that made us "weaker" as a whole. With joint pain and bad backs, we are not walking with an optimum gait nor proper posture. Over long periods of time, incorrect posture and positioning is no different than lifting weights with improper form. It exacerbates current injuries or creates new ones. That is why so many people have abdominal hernias, bulging or herniated discs, and deferred nerve pain.
I'm not even going to go into a discussion on what anyone should be doing in the gym. I am opposed to machine use personally. Sets, reps, and lifting regimen depend on what result you are wanting (raw strength or big, pretty muscles). There is a difference between being stronger and being bigger.
TL;DR - Yes, your leg muscles will be stronger than a person of normal weight but similar activity level.