The best replacement for gnome is kde.

The best alternatives to gnome are rated as following:
★★★★★  kde
★★★★  unity
★★★★  goblin engineering
★★  xfce
★  goblin
★  human warlock
★  human mage
★  dwarf
★  cinnamon
★  night elf rogue
★  kde opensuse
  human rogue
  lxde
  mate
  worgen warlock
  gnome classic
  troll
  kde desktop
  kde linux
  kde4
  gnome
  kde 2013
  elf
  kde ubuntu
  kde 4.1
  human warrior
  kde 4
  kds
  enlightenment
  gnome shell
  dwarf warrior
  halfling
  kde comparison
  cde
  gtk

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

Other search terms related to gnome and their ratings are:
★★★★★ evolution
★★★★★ xmonad
★★★★ pulseaudio
★★★★ i3
★★ hal
★★ awesome
★★ nautilus
★ ubuntu
★ fluxbox
★ gdm
★ network manager
★ openbox
You have in mind a companion for gnome and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of gnome in all years. Click on graph for more.
gnome
kde
unity