What third parties are better alternatives than the Democratic and Republican party?
There are no alternatives.
The way our system is setup, its either you vote right, or you vote left. There is no compromising-and our system is too engrained to change up now. Too many delegates, too many congressman, and too many people to educate. It would take ages upon ages to convince people that their are other options.
Accounting for 325 million people in America-if you look at the voter turnout for 2016, a little over than a quarter voted during D/R primaries (30%). With all of the loopholes, some states often vote on an open primary, or closed primary often restricting unaffiliated voters from voting for a 3rd party (L. Johnson, G. Stein).
When it comes down to it, if American voters decided to vote for someone different, how many Democrats or Republicans would be willing to risk their career to support a lesser majority?
The only option for 3rd party candidates is to creep their way inside the Red or Blue Parties in order to consider themselves a contested candidate. This is what Sanders did (was an independent), and this is what Trump did (Corporate Exec with no experience).
To note: Sanders didn't join the Democratic party until 2015 for his contested run as a Presidential nominee.