The best replacement for server 2012 is 2012 r2.

The best alternatives to server 2012 are rated as following:
★★★★★  2012 r2
★★  server 2012 essentials
★★  hyper-v server 2012
★★  whs 2011
★  freenas
★  windows server 2008
★  sql server 2008
★  sbs 2011
★  windows server 2012 r2
  storage server 2012
  2008 r2
  r2
  mysql
  server 2012 r2

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Speaking about server 2012, one probably shouldn't forget about hyper-v.

Other search terms related to server 2012 and their ratings are:
★★★★★ hyper-v
★★ ssis
★★ sharepoint 2010
★ visual studio 2010
★ business intelligence
★ hyper v
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server 2012
2012 r2
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