Is FormTitan a Gravity Forms alternative for creating Salesforce forms?

Sure it is.
Gravity Forms is a well respected form builder, however like any other form builder it has its pros and cons. in addition, every user has different needs and requirements, So when you need to make your call be sure to choose the tool that is best for you.
But just for this post, If we compare Gravity forms with FormTitan- you will see that FormTitan could most certainly be considered a Gravity Forms alternative:

Gravity forms:  For one thing - it is a form builder specially designed for WordPress. 
FormTitan: This is a versatile platform - its forms could be used on websites, blogs, wordpress, salesforce...
Gravity forms:: It does not support responsive forms
FormTitan:  Allows you to build responsive forms for desktop, tablet and mobile devices.
Gravity forms:: Need plugin
FormTitan:  Requires no download and no installations. Web tool with everything already built in.
Gravity forms:: Has no SSL security
FormTitan: Has SSL. in fact it was designed and built with security as one of its top priorities.
Gravity forms:: Has no A/B Testing feature
FormTitan: Has A/B Testing, heatmaps, CRO engine, conditional logic and other optimization tools.
Gravity forms:: Has a limited Salesforce integration where you can write data in SF but not read from SF records.
FormTitan: Has the most powerful Bi directional Salesforce integration

And these are only a few of the topics we've checked. Feel free to check out more FormTitan features