i'll give another vote to potholes reservoir...though it does seem to be having lots of problems with the spiny ray populations as well as moses lake in the last 10 years or so. last i checked they put in a 20 fish limit on perch at potholes. probably the guys at mar don trying to get the fish hogs off their docks(they'd have some people come and take 150+ perch in a good day).
i think the winds may be changing on this one though. i haven't caught a decent sized perch or bluegill at potholes in several years. maybe they just don't hang around the docks any more and you have to chase them into the dunes? i must say though, the smallmouth fishing more than makes up for it...the last time i was there i caught nearly 50 fish in less than 2 hours. i was fishing along the dam face and the smallies were literally taking my jig on every cast, as soon as it hit the water. you could cast it out and set the hook, and there would already be a fish on.
i fished the part of riffe lake where the cowlitz runs in back in august and did great on smallmouth and largemouth. right under the fishing bridge at taidnapam(?) park, it has a rocky basalt shoreline that just screams smallmouth on it.
as for westside spiny ray lakes, my favorite is probably hicks or st. clair. hicks is a good all around lake in the spring and fall, and st. clair has huge perch in it.