The best replacement for mp4 is mp3.

The best alternatives to mp4 are rated as following:
★★★★★  mp3
★★★★★  avi
★★★★  mkv
★★★★  m4v
★★★  wmv
★★  mov
★★  flv
★  mpeg4
★  avchd
★  mpeg
★  3gp
★  h.264
★  divx
★  webm
★  m4a
  mpeg 4
  avchd which is better
  h264
  h 264
  mpg
  aac
  mp4v2
  mp3 files
  ts
  mkv plex
  wmv file size
  wav
  mp3 player
  avi which is best
  mp5
  .mov files
  mpeg 2
  avi which is better
  avi file size
  3pg
  avc
  mp2
  mkv quality
  avi quality
  wma

Your alternative for mp4 is not listed? Suggest!
Speaking about mp4, one probably shouldn't forget about windows media player.

Other search terms related to mp4 and their ratings are:
★★★★★ windows media player
★★★ ac3
★★ srt
★★ windows movie maker
★★ subtitles
★★ mp3 audio
★ dts
★ windows dvd maker
★ imovie
subtitle
flowplayer
subtitles ps3
You have in mind a companion for mp4 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of mp4 in all years. Click on graph for more.
mp4
mp3
avi