Important as to what?
All of the exercises mentioned above are just DIFFERENT exercises. If you had to do one and hit most of the "important" muscles in the leg, it's squats.
Wes Norris, CSCS
gym coch listed, what i think, are the best leg exercises but if i were u liquid tension I would pick one or two and do those. i would go for squats and RDL or stiff legged dead lift.
romanian deadlifts are where the weights don't touch the floor again until you finish the set. So when you go down after each rep you don't let it touch the floor.
Romanian deadlifts are not stiff leg deadlifts, they're far from it. The hips move back, the bar travels down the thighs, and the head comes forward. The bar generally does not go past the knees or much further below the knees.