The best replacement for jquery ui is jquery.

The best alternatives to jquery ui are rated as following:
★★★★★  jquery
★★★★★  bootstrap
★★★★★  extjs
★★★★  dojo
★★★★  jquery tools
★★★  yui
★★★  easyui
★★★  kendo ui
★★  ajax control toolkit
★★  jqwidgets
  twitter bootstrap
  jquery mobile
  scriptaculous
  juice ui
  dijit

Your alternative for jquery ui is not listed? Suggest!
Speaking about jquery ui, one probably shouldn't forget about bootstrap 3.

Other search terms related to jquery ui and their ratings are:
★★★★★ bootstrap 3
★★★★ jquery mobile
★★★★ asp.net
You have in mind a companion for jquery ui and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of jquery ui in all years. Click on graph for more.
jquery ui
jquery
bootstrap