The best replacement for iis is apache.

The best alternatives to iis are rated as following:
★★★★★  apache
★★  tomcat
★★  iis express
★  nginx
★  weblogic
★  pws
★  websphere
★  apache market share
★  wamp
★  was
★  nginx performance
★  windows service
★  asp.net
★  apache security
★  xda iii
★  self hosting
★  apache php
  apache performance
  ti 30xa
  apache server
  xampp
  ti-34 multiview™
  personal web server
  jboss
  sharepoint
  windows server
  ihs
  wcf
  iii
  o2 xda iii
  cassini
  isa
  linux apache

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

Other search terms related to iis and their ratings are:
★★★★★ php
★★★★★ asp.net
★★★★ tomcat
★★★ mysql
★★ asp
★★ ssl
★ apache
★ multiple websites
★ dns
★ ftp
★ nlb
★ xp home
★ windows server 2008 r2
★ jboss
★ weblogic
★ arr
.net 4.5
windows server
jsp
windows server 2008
windows vista
websphere
.net
sql server
perl
asp.net configuration
You have in mind a companion for iis and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of iis in all years. Click on graph for more.
iis
apache
tomcat