I think lumens is the standard these days, but even then you're not sure what you are getting. Is it max lumens or usable lumens?

And then there seem to be a few ranges that are important:
Damn that's bright,
Hot Damn that's bright,
OMFG that's bright
and lastly turn that damn light off you're blinding me.

These correspond to 300 lumens, 600 lumens, 1000 lumens and 1500 lumens.

But really, if you haven't looked in a while, they are so much brighter than before and you can get some really cheap ones that'll outshine anything available just last year. The one I have is $34 and is rated at 1200 lumens, but I'd say it is an effective 600 or so. It doesn't matter as it is still a lot of light for the buck.

http://www.ebay.com/itm/251060235556...84.m1497.l2649