The best replacement for underscores is dashes.

The best alternatives to underscores are rated as following:
★★★★★  dashes
★★★★  bones
★★★  roots
★★  spaces
★★  hyphens
★  dashes seo

Your alternative for underscores is not listed? Suggest!
Speaking about underscores, one probably shouldn't forget about spaces in filenames.

Other search terms related to underscores and their ratings are:
★★★★★ spaces in filenames
★★ spaces
You have in mind a companion for underscores and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of underscores in all years. Click on graph for more.
underscores
dashes
bones