I use to run 2-3 times a week, before I got into bodybuilding. Running kept me in the 160-170 lb range at 5'9" - looked good, but average. No doubt in my mind that running is, at least for me, the most cardio intensive exercise - and it definitely eats fat and muscle. Now I weigh about 205, and for the past 2 years my favorite cardio has been the stairclimber - the one with the revolving staircase (like a real set of stairs set in motion). I do that 2-3 times a week and the fat stays off and I keep the muscle.
Long story short - I like the stairclimber best, then probably the bike, and last the treadmill.
DrG