The best replacement for gex is utx.

The best alternatives to gex are rated as following:
★★★★★  utx
★★★  rex
★★★  orbx
★★★  ftx
★★  fs global
★★  fscene
★  pbw
★  utx fsx
★  ultimate terrain
  megascenery
  gumball

Your alternative for gex is not listed? Suggest!
Speaking about gex, one probably shouldn't forget about orbx.

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



Google Trends

Scale is based on the average worldwide traffic of gex in all years. Click on graph for more.
gex
utx
rex