2nd try at recommending the Rim Rock; it's whistler's signature restaurant, has great seafood, and it's local cuise unlike the steakhouses which are chains.
The sushi at whistler is good, not too pricey, but not as good as you'd find in vancouver if you went to one of the better places in Van. If you're going big on every meal I'd skip the sushi and eat at the fairmont the night after the rim rock, but it's not a bad choice for medium priced. A drink at the Mallard room in the Fairmont is a must do, it's a gorgeous setting.
Thanks for the suggestion. I'll definitely hit up Rim Rock. The menu looks good.