No one is symmetrical...everyone has a larger side...ever notice one shoe is always tighter(my observation anyway...maybe I'M lopsided!)? Clothing and patterns are the same size on both sides. If these are pants that you sew yourself, you can try making the left side a little larger and see if the crease falls more evenly. Otherwise I don't know what you could do for store bought, as the old crease would probably show if you tried to press a new one. Maybe if there's enough seam allowance, you could let the left side out a bit and see if that helps.

Sounds like the fabric wasn't straight when it was cut. Dangle a length of string with a small weight on it over the center of your leg where you want the crease while wearing the pants. Have someone put pins on that straight line down the pant leg. Baste a line following the pins. Make a crease along that baste line. Now iron. That will make the leg SEEM to be straight......noting that the side seam/s now won't be straight....alas. Let us know. Salena