The best replacement for iphoto is aperture.

The best alternatives to iphoto are rated as following:
★★★★★  aperture
★★★★  picasa
★★★  lightroom
★★★  photoshop
★★  photoshop elements
★  imovie
★  shutterfly
★  lightroom 5
★  image capture
  elements
  photos
  adobe bridge
  folders
  aperture 2
  photoshop elements 12
  photoshop elements 9
  adobe photoshop
  pictures folder
  adobe elements
  iview
  mypublisher
  snapseed
  finder
  photoshop elements 10
  aperture 3
  photoshop elements 6
  canon software
  aperture library
  photo stream
  elements 9
  photo booth
  lightroom 4
  picasa for mac
  blurb
  pixelmator

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

Other search terms related to iphoto and their ratings are:
★★★★★ dropbox
★★★★ icloud
★★★ google drive
★★★ photostream
★★ snapfish
★ importing
★ import
★ raw
★ importing photos
★ picasa
You have in mind a companion for iphoto and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of iphoto in all years. Click on graph for more.
iphoto
aperture
picasa