If the filets are OK in terms of color and smell, cook them right up and instead of serving as is, make a salad by lightly flaking the cooked salmon, adding mayo and lemon juice to taste, then some finely diced preserved lemon and/or onion, and a bit of freshly ground pepper. I have done this with frozen arctic char that was past its prime and it was surprisingly good.

I agree with above. You mIght want to try this recipe...it's delicious and would hide any textural problems.
http://food52.com/recipes/4550_leftover_salmon_kedgeree

I've made it without curry and it was still delicious.

I think the 2 previous answers are right in the cook and smell test. But you might not want to serve as a fillet. I haven't tried this particular recipe, but ochazuke is a very simple dish where the broth covers some texture or other problems that may occur.

http://food52.com/recipes/4534_salmon_ochazuke_tea_rice

Picture to die for...

Just cook it. Best case, you have salmon. Worst case, you have no salmon.

How are they packaged? Are they in plastic freezer bags, or are they vacuum sealed?

If they're vacuumed sealed, I'd try to use them. Defrost them in a cold water bath and see how they look. If the color is good- ie not gray- and they smell fine, I'd use them. If they are in plastic freezer bags, defrost in the fridge. Check color and smell before making a decision.