I have a fish pond with a waterfall just outside my bedroom windows, and during the warm months that is the sound I hear as I fall asleep. For a while the pond was under seige by raccoons, who were attacking the fish and plants, which required me to get up to chase them away, so I found myself waking up at the slightest change in sound for a long time afterwards, even after I devised raccoon control methods (mainly, electric fence wire around pond). So now the waterfall sound is soothing again.
In the winter with the windows closed I don't hear the waterfall much if at all. But it's a very quiet location, even though it's just off downtown, so I don't really need white sound.
Somewhere along the way I bought a little sound generator - waves, rainforest, etc. But once I noticed that the sounds repeated every 15 seconds or so with a slight but detectable break, it ceased to be sleep-inducing. But the ocean waves I ound the most soothing. For a while I put the sound generator in a protected location by the fish pond, so people would hear tree frogs as they walked by.
Also have a Timex CD/radio/clock with sound generator, but it just couldn't compete with the waterfall ;-).