riding on a dark bike path..., I would think that seeing the path and any obstacles well is most important. you could get a 180 lumen flashlight, like the Fenix L2D, LD20, or similar, or the Magicshine which gives you the option of even more light if you need or want it. I have bike path sections on my commute where I can surprise a skunk, so having a good light helps me prevent a smelly situation by stopping/slowing in advance. So, it depends on your conditions, how fast you want to ride, etc... Remember to aim the light at a point on the ground perhaps 20-30 ft in front of the bike so as not to blind others.
That's the other part about rating lights, it's not just the optical power produced, but the dispersion pattern the light is produced in. You want more light illuminating the road, and less blinding others, just like car headlights have been designed to do.