Cycling is probably the lowest impact exercise, so if you have problems with your knees bearing impact/weight that's the one.
Rowing is also low impact and is basically a full body workout.
Treadmill is running, it's considered high impact normally, but with how they're built to cushion impacts and have suspension systems, you can consider it medium impact or lowish.
Treadmill is about the only one that forces you to exercise while the others are based off of your movements activating the machine itself. That is unless you have a manual treadmill.
They all do fine for losing weight.
I can't think about anymore.
It depends on what you want. If you want general fitness rowing sounds great (I've never rowed myself). If you want lung capacity then look at the treadmill or the bike. Cycling gives you really ripped legs if you do it consistently. Treadmill builds up endurance so you can do things yourself. Imagine being able to think you can run 13 miles straight without stopping. Or if you REALLY needed to get somewhere you could do 2 miles in about 20 minutes or less on your own without needing a bike or car.
They're all valid dependent on what you need. I love both cycling and running. I have to say having a high cycling endurance you can do 30-60 miles outdoors and REALLY see your area and learn it. However...you have to hope drivers are nice to cyclists which they aren't to do that.
[05:45:34] I bought an American L and it was like a tent