The best replacement for orks is tyranids.

The best alternatives to orks are rated as following:
★★★★★  tyranids
★★★  necrons
★★★  tau
★★  eldar
★★  chaos
★★  space marines
★★  orcs
★  imperial guard
★  tyranids tactics
★  grey knights
★  krogan
★  chaos space marines
★  space wolves
  dark eldar
  dark angels
  imperial guard dawn of war
  eldar tactics
  nids

Your alternative for orks is not listed? Suggest!
Speaking about orks, one probably shouldn't forget about space marines.

Other search terms related to orks and their ratings are:
★★★★★ space marines
★★★ dark eldar
★ space wolves
You have in mind a companion for orks and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of orks in all years. Click on graph for more.
orks
tyranids
necrons