If you have a painted wall, I have found pretty good success with Formula 409. You'll need to apply it full strength, and saturate well. Depending on how large an area you're doing, this could get a bit expensive. My mother use to use an product called Spic-N-Span, which was a powder that you mixed with a bucket of warm water. I don't even know if it's still on the market, but it's much less expensive, and works particularly well with an old-fashioned scrub brush.
Warning: Either way, you'll probably want to repaint, but at least you'll have a nice clean surface.