The best replacement for server 2008 r2 is 2008.

The best alternatives to server 2008 r2 are rated as following:
★★★★★  2008
★★★  windows server 2008
★★  sql server 2008
★  server 2008
★  enterprise standard
★  sbs 2011

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Speaking about server 2008 r2, one probably shouldn't forget about hyper v.

Other search terms related to server 2008 r2 and their ratings are:
★★★★★ hyper v
★★★ management studio
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server 2008 r2
2008
windows server 2008