Google Authenticator, but only because it's the only I have used.
Are there any other ones that are actually better?
there is, authy is pretty good, if you are poor and can't get even a economic smartphone and you are stuck with old standard phone, also i like the sms code, it's easy and fast
Authy is much less secure than most of the others and you are dependant on the Authy service. If anything happens to the Authy service you are SOL.
Google authenticator (and every other app that implements TOTP) isn't dependant on anything, it's stand-alone so even if Google were to disappear your app will continue working fine, with Authy you'd be fucked.
Also Authy has the ability to bypass 2FA on any of your accounts, so if there is a rogue employee or they are hacked then it could lead to many people being hacked.
And there are privacy issues as Authy knows when you are logging in, what websites you are logging into, what other Authy-enabled websites you use and your phone number and your IP. You also must disclose your phone number to them to use the service.
Not only that large website owners have to pay Authy a fee to use the service, which is ridiculous when there are so many free and open source solutions that are far superior to Authy.
There are TOTP clients available for older phones, I know symbian phones have one and I'm sure any of the old feature phones that run Java could run a client, though I don't know if anyone has taken the time to code one up.