Space Needle is ok for a view of the city and water, however, be prepared for several people stopping in front of you for pics, rude ppl talking over the guides in the elevator, and too crowded conditions.
Chihuly, however, is NOT to be missed. The use of lightning with extraordinary glassworks, garden and flowers combined with just the right glasswork, music outside, a classy cafe, glass blowing demo, complimentary photographer, films, and great giftshop, and you have a winner. My favorite activity in Seattle, hands down.