The "blinky"-type lights are "be seen" rather than "see by" lights. Lights that'll let you see a useful amount are generally in the 100+ lumen range (I think it's 150 or 175), and they're pretty expensive. If you're riding in a well-lit area, you might be able to get away with a less-powerful light.

I have a small NiteRider light that's reasonably bright, and a Performance house-brand 3-LED light, but I'm riding on trails that I know well and are decently free of stuff, for the most part. There's a 4- or 5-LED version that is well-recommended by the people I ride with. I might have to upgrade. All three of these, though, are "see me" lights.

I think NiteRider makes higher-powered stuff too that you can see by.