I use google authenticator for 2fa validations, I am very happy with it, it has an easy interface and so far i didn't have any problems related to safety.
I dont see there is any alternative for google app for 2fa authentication and most of the exchanges are having this pre loaded. Its the best solution to stop the hacking most of the time.
Nearly all exchanges favor Google 2 FA in secure authentication. Besides Google 2FA, there are other good apps like Authy. but does not mean that it will replace the reputation and credibility of the Google 2 FA. Just back up your backups to a safe place.