The best replacement for s4 is s5.

The best alternatives to s4 are rated as following:
★★★★★  s5
★★★★★  m3
★★★  htc one
★★★  note 3
★★★  iphone 5
★★★  s4 mini
★★  5s
★★  s4 active
★★  note 2
★★  s3
★★  rs4
★★  g2
★★  335i
★★  nexus 5
★★  a4
★  iphone 5s
★  bmw m3
★  335
★  moto x
★  sti
★  iphone 5c
★  mega
★  droid maxx
★  lg g2
  wait for s5
  note 3 specs
  iphone
  wrx
  5c
  a5
  a6
  335xi
  s5 rx7
  335is
  s6
  z1
  note
  bmw 335i
  s4i
  c55
  e36 m3
  ns7
  4s
  s10
  gunz
  xperia z
  audi s6
  5s specs

Your alternative for s4 is not listed? Suggest!
Speaking about s4, one probably shouldn't forget about itunes.

Other search terms related to s4 and their ratings are:
★★★★★ itunes
★★★★ galaxy gear
★ gear
You have in mind a companion for s4 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of s4 in all years. Click on graph for more.
s4
s5
m3