The best replacement for buffy is angel.

The best alternatives to buffy are rated as following:
★★★★★  angel
★★★★  dracula
★★★  edward
★★★  faith
★★★  twilight
★★  charmed
★★  glory
★  supernatural
★  vampire diaries
★  blade
★  xena
★  angel better
★  willow
★  bella
★  firefly
★  true blood
★  veronica mars
  aqua mirabilis
  cordelia
  cherokee
  spike
  x files
  cullen
  selene
  edward twilight
  angel first
  caleb
  ki toy

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

Other search terms related to buffy and their ratings are:
★★★★★ spike
★ angel episodes
buffy
spike fanfiction
You have in mind a companion for buffy and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of buffy in all years. Click on graph for more.
buffy
angel
dracula