The best replacement for gpg is pgp.

The best alternatives to gpg are rated as following:
★★★★★  pgp
★★★  ppm
★★★  openssl
★★★  gpg2
★  openpgp
★  smime
★  gnupg
★  truecrypt
  axcrypt

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

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



Google Trends

Scale is based on the average worldwide traffic of gpg in all years. Click on graph for more.
gpg
pgp
ppm