The best replacement for x264 is xvid.

The best alternatives to x264 are rated as following:
★★★★★  xvid
★★★  mpeg4
★★★  h264
★★  divx
★★  ffmpeg
★★  x265
★★  nvenc
★  h 264
★  nvidia nvenc
★  ac3
★  h264 which is better
★  quick sync
★  xvid better
★  avc
★  vp9
  xvid quality
  mpeg 2
  nero avc
  mainconcept
  vp8
  lagarith
  mencoder
  mpeg4 codec
  h263p
  avchd
  mpeg2

Your alternative for x264 is not listed? Suggest!
Speaking about x264, one probably shouldn't forget about virtualdub.

Other search terms related to x264 and their ratings are:
★★★★★ virtualdub
★★★ ffmpeg
★★ gordian knot
★★ mencoder
vdub
You have in mind a companion for x264 and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of x264 in all years. Click on graph for more.
x264
xvid
mpeg4