I've always followed the rule, prepare for the most likely event.
But then, I also think you really don't need to have any specific disaster in mind to prepare for. So my philosophy is just to cover the general necessities and be flexible with everything else, because no matter how much you try and prepare for, chances are you're never going to cover it all. The good thing is, just a few basics like water, food and money can cover almost any situation, from flood, earthquakes, ice storms, blackouts, terrorist attacks, riots, interruption of services, etc. The same items stored in a car would cover almost any instance where you'd be stuck in your car, like a breakdown, blizzard, evacuations, etc. I don't think it really matters what the problem is, the basics remain the same.

In terms of probability, I'd guess that most of the problems that people need to prepare for are personal (local) problems, not the widespread natural disasters like Katrina or a mega tsunami. Financial hardship would probably rank #1 in terms of probability, followed by theft and fire (as you probably found out). A decent fire safe with some extra savings inside would be a good preparation for any of those situations, and could also be considered a long term preparation. IF you were forced to bug out, at least you would have some comfort in knowing that the things you left behind would be somewhat protected from the average looter and might still be there when you return. I've gone through a small house fire, and a good fire safe quickly became the #1 purchase.

In my case, I'm lucky that I really don't buy any items specifically for preparing. I already have camping and hiking supplies, but I buy them for personal use, the fact that they might be useful in an emergency is just an added benefit. Honestly, I don't think it's a good idea to spend a lot of money on items you don't use, because if you're not using it now, the chances are you're not gonnna use it in the future either. That money would be better spent purchasing extra things that you currently do use.