Well,
Greg's Cycles is the biggest around. Locations in Greenlake, Bellevue, and on Aurora. I prefer the Greenlake location. Just a little more professional, not as many high school-age employees. I have not dealt with their service department, though I have heard them comment that simple tune ups can be as long as 3weeks during peak season. Product lines include Bianchi, Trek, Specialized, Descente, Rudy Project (sunglasses).
I really like
Sammamish Valley Cycle out in your neck of the woods. I bought my Virata from them this last Spring. Very good experience. I do most of my own wrench work so, again, no experience with their service department. Product lines include Bianchi, Serotta, Cervelo, Assos, Smiths (sunglasses).
I guess it really depends on what you are looking for. A new bike? Vintage bikes? Or just some accessories and the occasional tune-up/overhaul? Do not forget REI. Not the greatest selection, but occasionally better prices.
-José