The stair master is my go to cardio machine now. One thing you could do for better gains is to spice it up with high intensity intervals. Like on the stairs master, I will crank it up to 16 for a minute, and then dial it back down to 4 for a minute while I recover. I repeat that for 30 minutes.
On the treadmill, I crank it up to 10 or 11 for a minute, and slow it back down to 3 for a minute while I recover.
Outside I primarily work on sprints instead of light jogs. I don't consider a cardio workout effective unless I'm about to fall over gasping for air when I'm done.