The best replacement for backer board is cement board.

The best alternatives to backer board are rated as following:
★★★★★  cement board
★★★★  green board
★★★  drywall
★★★  plywood
★★★  wonderboard
★★  ditra
★★  hardibacker
★  mortar bed
★  durock
★  cement
★  wire mesh
  ply
  wonder board
  durarock
  greenboard

Your alternative for backer board is not listed? Suggest!
Speaking about backer board, one probably shouldn't forget about vapor barrier.

Other search terms related to backer board and their ratings are:
★★★★★ vapor barrier
You have in mind a companion for backer board and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of backer board in all years. Click on graph for more.
backer board
cement board
green board