The best replacement for fancybox is lightbox.

The best alternatives to fancybox are rated as following:
★★★★★  lightbox
★★★  prettyphoto
★★  colorbox
★★  shadowbox
★★  bootstrap modal
★  thickbox
★  facebox
  almabox

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

Other search terms related to fancybox and their ratings are:
★★★★★ thumbnails
★★★★★ vimeo
★★ popup
You have in mind a companion for fancybox and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of fancybox in all years. Click on graph for more.
fancybox
lightbox
prettyphoto