I remember when I was younger and management would send out employee opinion surveys. I'd answer them, be truthful and feel like my opinion actually mattered. I felt it was proper to express exactly how happy or unhappy I was and that the survey was some mechanism for improving things.
Then I became part of management and I realized how completely wrong I was.
The employee opinion survey mostly serves as a crutch for manager's to pat themselves on the back and the do a very good job curve fitting the results to their preconceived notions of how things are. It also serves to weed out people with bad attitudes - I've overheard more than one discussion of trying to locate an employee based on the comment they made on the survey.
So, if you say you're happy with the wage you're getting, you won't be getting a raise. In fact, it's even seen as a sign that pay cuts should be happening. Likewise, if you feel like you're a valued employee, good luck getting any more benefits. It's more likely management will use that as an excuse to strip away that one little perk, like free soda or something, just because they'll decrease the amount of HR budget dedicated to keeping employees happy. Don't ever be happy on paper.
Unfortunately, it's not enough for just you to express your desire for a raise. If 40% of your colleagues think they get paid enough, that's probably enough for management to little to no wage increase. You really want less than 5 - 10% say they're happy - in other words, 90% of the employees in your department need to express displeasure with their wages in order for the survey to have any meaningful effect on wages. (There's plenty of other ways to get a raise though - an employee survey is probably one of the least likely ways for it to happen.)
PS. If you think your company is one of those awesome companies that cares, you're probably wrong. If you sat in the room with the CEO, COO, and HR Director and heard that private conversation about the survey, you'd be horrified.