The best replacement for flv is mp4.

The best alternatives to flv are rated as following:
★★★★★  mp4
★★★★★  swf
★★★★  f4v
★★★★  avi
★★★  wmv
★★  mov
★  fla
★  mkv
★  h.264
★  mp4 better
★  webm
★  swf files
★  mp4 which is better quality
★  olv
★  avi which is better
★  mp4 quality
★  f4v better
  mp4 which is better
  3gp
  swf which is better
  mp4 size
  mkv better
  divx
  flc
  mp4 compare
  quicktime
  swf flash
  swf better
  m4v
  mp4 file size
  avi better

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

Other search terms related to flv and their ratings are:
★★★★★ vlc player
★★★★ swf
★★★ cue points
You have in mind a companion for flv and it is not yet here? Propose!



Google Trends

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