What pier are you leaving from? If it's 90 or 91, you won't be in the central downtown Seattle area. Those piers are a 15 minute or so cab ride north from downtown. Unfortunately, not a lot I can think of within walking distance from that pier. It's not really a tourist area.
However, if you are stopping in downtown first, then yes, there are some great places to eat! The Crab Pot is noisy and busy, but fun. I haven't eaten there personally, but have many friends who have and have been by it several times. Depending how much you want to spend, what kind of food you like, and how far you want to travel, I can make recommendations.