The best replacement for derailleur is hub.

The best alternatives to derailleur are rated as following:
★★★★★  hub
★★★  internal hub
★★  rohloff
★★  105
★★  clamp on
★★  short cage
★  gs
★  bottom swing front derailleur
★  shimano
★  shimano derailleur
  exage 500 derailleur
  hub gear
  rapid rise rear derailleur

Your alternative for derailleur is not listed? Suggest!
Speaking about derailleur, one probably shouldn't forget about shimano shifters.

Other search terms related to derailleur and their ratings are:
★★★★★ shimano shifters
★★★★★ shimano cassette
★★★ 9 speed shifter
★★★ internal hub
★★★ sram shifters
★★ shimano shifter
★★ campy shifters
★★ 105 shifters
★★ horizontal dropouts
★★ tiagra shifters
★ campy cassette
★ shimano crankset
★ 8 speed chain
★ friction shifters
★ 10 speed shifter
★ 9 speed chain
★ campagnolo cassette
road shifters
nine speed chain
sram shifter
You have in mind a companion for derailleur and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of derailleur in all years. Click on graph for more.
derailleur
hub
internal hub