I'm consolidating a couple of the items listed that seemed to be saying more or less the same thing. Also remember, you get THREE and ONLY THREE VOTES. Those who voted for more, I grabbed your topmost three.
I'm also voting for fixing the morale system. In more detail, it seems that there should be two scales of emotional states. I suggest Contement/Discontentment, Happiness/Saddness. For contentment, you'd have thoughts for room quality and luxury (or lack thereof), and for happiness you'd have more serious things, like deaths/births, masterpeice loss/creation, etc.
Contentment level would determine the reaction to being happy or sad. A discontent mourner might commit suicide, or in extreme cases commit murder. A content mourner would just sulk for a while. A happy but discontent dwarf might be interested in revolutionary actions, like tantrums and sabatoge. A happy and content dwarf would get a bonus to productivity.
Thoughts should also decay at a variable rate, not just be there for a while and vanish suddenly one day. Some thoughts should be MASSIVELY severe at the start, and then decay just as rapidly, but linger at a low level for a while (like death). Some thoughts could actually grow over time until fixed (such as discontentment over room quality). Some thoughts should just decline at a linear rate (such as appreciating good craftsdwarfship).
My second vote will go to Fixing Farming. There's a thread devoted to this. I prefer the more realistic options of requiring a lot more farmland to feed your dwarves, which might make trading for food a better option and would also make sieges scarier (if you can't get outside, you won't be eating long...) but I'd like anything to make food a CHALLENGE.
I'll reserve my third vote for now...