I think the most important thing for self-defense is confidence, poise, and the ability to recognise when it's needed. Any system can give you this if you have the right teacher.
i'm learning the hung gar system popularised by frank yee, and i think it's a good system for self defense. There are elements of tiger, crane, snake, leopard, and dragon in this system, as well as some drunken, monkey, chin-na, grappling (can't remember how to spell "shuoi jiao"), incorporated into it.
It develops both internal and external, has both hard and soft, and is a complete system. There aren't much in the way of high kicks but for self-defense i don't know how important that is.
Most importantly thought, it's developed my spirit and confidence so that now, in unpleasant situations, I have the peace of mind knowing that I can handle it - and if I can't, my wife can - she takes hung gar too