The best replacement for 4gb is 8gb ram.

The best alternatives to 4gb are rated as following:
★★★★★  8gb ram
★★★★  8gb
★★★★  6gb
★★★  250gb xbox
★★★  250gb
★★  8gb macbook pro
★★  8gb memory
★★  6gb ram
★★  8gb macbook air
★★  2gb
★  2gb gtx 770
★  8gb gaming
★  8gb surface pro 2
★  2gb graphics card
★  250gb xbox 360
★  2gb gtx 760
★  2gb gpu
★  8gb laptop
★  8gb ram macbook pro
★  2gb 770
★  2gb ram
  2gb video card
  250 gb
  2gb vram
  8gb windows 7
  8gb macbook
  2x2gb
  8gb of ram
  6gb memory
  xbox 360 250 gb
  xbox 360 250gb
  250gb xbox slim
  2gb xp
  8gb ddr3
  512mb
  3gb
  8 gb
  250 gb xbox
  8gb mac
  ipod nano 8gb
  iphone 8gb
  12gb ram
  250gb xbox kinect

Your alternative for 4gb is not listed? Suggest!
Speaking about 4gb, one probably shouldn't forget about xp.

Other search terms related to 4gb and their ratings are:
★★★★★ xp
★★★★ 2gb sli
★★★★ nvse
★★★ 32 bit windows
★★★ 2gb ram
★ 2gb
ready boost
You have in mind a companion for 4gb and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of 4gb in all years. Click on graph for more.
4gb
8gb ram
8gb