No, you don't. They told me the same thing when I bought my S3. But what they mean is you need a google account. And you can certainly have that without gmail, which is just Google's email service.
I was wondering about that while I was responding. Just assumed it was a whole package deal. If someone is going through the time to setup a Google account, they might as well setup a gmail account too while they're at it, but didn't intend to misinform.