If you're riding on bike trails with oncoming traffic that's bikes and pedstrians right in front of you, I think the Phillips Saferide is the best battery light you can get:
http://www.amazon.com/Philips-SafeRi...llips+saferide

It has a cutoff like a car headlight, and an evenly shaped so, so it doesn't get into people eyes and a bright spot in the beam doesn't diminish your eyes ability to use the light (your eyes adjust to the brightest light around you, a light with a super bright spot causes your eyes to adjust and not use less bright light as well). If you buy one, the built in charger in the light is very good, but the batteries it comes with have a bad reputation - buy AA rechargeables like eneloops.

It's drawbacks are that it's not as wide as some other higher powered lights (though it's still pretty good), and it's runtime is 1.5 hours on high.

If you are not heading directly towards oncoming traffic on a trail, and instead your priority is flooding the road with light, I really like the Light And Motion Taz:
Light and Motion Taz 1200 Lumens Bike Light | Amazon.com: Outdoor Recreation

It also has very good light output, and throws out so much light it overcomes any bad lighting conditions for me, including the worst paths for bike lighting I've run across. The color temp and distribution of light it puts out is also very good, it looks very natural and it's easy to see with. Downside is mainly a lower runtime - 1.5 hours on high.

There are also numerous far, far cheaper lights on amazon as well, I'm just not as familiar with them. They usually put out crappier light quality, and you have to find out that doesn't have a bad hotspot, and they're not as reliable or waterproof. But, they're also 10x cheaper or something.