We've been on two cruises and I way-overpacked for both of them! Didn't wear half of the stuff I brought, even though one was 14 days and the other was 10.

Here's how I would (hopefully) pack for a cruise now. For 7 days:
2 pairs of capris and 3-4 tops to match...I'd probably bring 3 short sleeve cotton tops for shore excursions and one 3/4 length sleeve in case of cooler weather;

1 pair of long pants (but I would actually have 2 pairs because I'd wear a different pair on the plane...that airplane pair of long pants is convertible to capris, so that actually gives me the third pair of capris as well as the 2nd pair of long pants, though they're jean-type and not at all dressy) and 2 tops - one slightly dressier and the other long-sleeve;

good walking shoes - I have to wear orthotics, so always wear sneakers on the plane, and pack a pair of comfortable walking sandals;

for a 7-day cruise, pack one complete outfit for the formal night if you're planning on eating in the dining room. I take a long lightweight black velveteen skirt and 2 dressy tops; add dressy sandals, jewellery, and a pashmini (I also pack a dressy black velveteen sweater) to match.

Because I get cold easily, I also wear one sweater-that-goes-with-everything and a jacket on the plane...my usual travel jacket's lightweight, rainproof and goes with almost everything, and has been indispensible on every trip I've brought it on.

[Sidestory about the jacket - in Morocco, there were about 25 people in our group, trying to weave our way through the narrow cobblestone streets of a very crowded medina (a marketplace labrynth!). Our tour leader led at the front, but the people in the back could never see him in all the crowds (people and donkeys!). So I ended up sticking myself in the middle of the group, and held my yellow-coated arm and umbrella in the air for the entire morning's tour. The people in the back constantly remarked how grateful they were for that bright yellow jacket.]

I would also include a shorter skirt, again for shore excursions/shopping, but I rarely ever wear them, I usually just wear capris.

And don't forget at least one bathing suit and cover-up (to get from the room to the pool). And sunscreen.