The best replacement for oauth is openid.

The best alternatives to oauth are rated as following:
★★★★★  openid
★★★  saml
★★  oauth2
★★  omniauth
★  hmac
★  basic auth
★  ldap
★  ssl
★  sso
★  cas
★  kerberos
★  xacml
★  oauth
  xauth
  http basic
  persona
  oauth 2
  jwt
  authsub
  shibboleth
  sts

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

Other search terms related to oauth and their ratings are:
★★★★★ twitter
★★★ callback url
sso
You have in mind a companion for oauth and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of oauth in all years. Click on graph for more.
oauth
openid
saml