正直に言えば=to tell the truth, ...
There are often ellipsis in Japanese.
For example, if you say "しょうじき", they think you want to say "正直に言えば".
Examples that the Japanese would not use:
To be honest, these are the statements I got from the translator. You can see that these three expressions are very written.
"しょうじき" is the most commonly used. You can often see it in Anime and Japanese TV series.