The best replacement for inkscape is illustrator.

The best alternatives to inkscape are rated as following:
★★★★★  illustrator
★★★  gimp
★★  adobe illustrator
★★  corel draw
★★  xara
★  coreldraw
★  idraw
★  paint.net
★  sketch
  scribus
  krita
  drawplus
  corel
  dia
  openoffice draw
  synfig
  tikz
  sodipodi
  karbonn

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

Other search terms related to inkscape and their ratings are:
★★★★★ bamboo
★★★ sure cuts alot
★ ghostscript
You have in mind a companion for inkscape and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of inkscape in all years. Click on graph for more.
inkscape
illustrator
gimp