The best replacement for akamai is limelight.

The best alternatives to akamai are rated as following:
★★★★★  limelight
★★★★  edgecast
★★★  level 3
★★★  cloudflare
★★★  cloudfront
★★  firstly
★  incapsula
★  prolexic
★  amazon cloudfront
★  cdnetworks
★  azure cdn
★  brightcove
★  maxcdn
★  amazon s3
  highwinds
  cachefly
  amazon web services
  limelight networks
  amazon cdn

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Speaking about akamai, one probably shouldn't forget about adobe.

Other search terms related to akamai and their ratings are:
★★★★★ adobe
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Google Trends

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akamai
limelight
edgecast