The best replacement for compiz is metacity.

The best alternatives to compiz are rated as following:
★★★★★  metacity
★★★★★  beryl
★★★★  kwin
★★★★  compiz fusion
★★★  emerald
★★  openbox
★★  mutter
★★  compton
★  aero
★  xfwm
★  gnome 3
  xgl
  xcompmgr
  clutter
  compiz-fusion

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

Other search terms related to compiz and their ratings are:
★★★★★ xfce
★★★★ openbox
★★★★ kde
★★★★ unity
★★★★ mate
★★★ emerald
★★★ fluxbox
★★★ gnome 3
★★ xfce4
★★ gnome shell
★★ lxde
★★ metacity
★ lubuntu
xgl
xmonad
You have in mind a companion for compiz and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of compiz in all years. Click on graph for more.
compiz
metacity
beryl