The best replacement for cs3 is cs5.

The best alternatives to cs3 are rated as following:
★★★★★  cs5
★★★★★  elements
★★★★  cs2
★★★★  cs3 extended
★★★★  cs4
★★★  af31
★★  lightroom
★★  dyna comp
★  cs2 boss
★  zvox 580
★  cs6
★  dreamweaver 8
★  elements 9
★  photoshop 7
★  photoshop cs3 extended
★  photoshop elements
  flash 8
  elements 6
  expression web
  photoshop cs4
  zvox
  aperture
  gimp

Your alternative for cs3 is not listed? Suggest!
Speaking about cs3, one probably shouldn't forget about snow leopard.

Other search terms related to cs3 and their ratings are:
★★★★★ snow leopard
lightroom
You have in mind a companion for cs3 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of cs3 in all years. Click on graph for more.
cs3
cs5
elements