I did originally intend to use the Roosevelt 'Infamy' recording, but it's actually rather noisy if you listen to the entire thing, with a lot of what I presume are mike noises and general clutter. I even tried quite a lot of filtering, compression etc to try and clean it up, but in the end, it just wasn't gonna fly. And I daresay the truth is that the reason the 'a day that will live in infamy' sound bite is heard so often, is that it's one of the few clutter-free parts of the address. The full length address is actually rather long-winded too. Although it does use some quite clever speech techniques, ironically in fact, techniques that Hitler also used, such as repeating things three times etc. Well worth seeking out for a listen if you've never heard it in its entirety.
Roosevelt does make good points in it, most notably the fact that while the Japanese were still attempting to appear to offer an olive branch to the US in the negotiations which took place immediately prior to the strike on Pearl Harbor, it was quite apparent (especially to anyone who's sailed their sub from Pearl to the Japanese coast in SH4), that the attack must have been planned months beforehand, simply based on the transit time across the Pacific. It's a point well made, given that he is asking for approval to declare war from the American people, in that it underlines the callous treachery behind the attack.
Back on the subject at hand however, my original plan was not dissimilar to what you suggested - i.e. to recreate some of the attack sequences with the flight sim Pacific Fighters and overlay it with excerpts from that famous address and some news announcements, and I did actually record FRAPS footage of some Japanese attack aircraft and do a rough edit to try it out. But without the planned overdub of the Roosevelt address in a usable form, I thought it came across a bit lame. Besides which, everyone knows what happened on that day, and referring to it briefly in the 'newsreel' version, while showing a sub setting sail for retribution seemed to be more fitting. After all, SH4 is a submarine sim, not a torpedo bomber flight sim.
If you disagree, you could of course have a bash at producing a replacement intro for yourself. All you really need is FRAPS (or similar), the movie editing app that comes with windows and a sound editing app, not that much at all really. I certainly enjoyed having a crack at it, and as you can see from this post, there are a lot of things to consider (especially my bad acting), so it presents a good challenge, why not give it a try yourself?
Incidentally, the other famous recording of Roosevelt: 'The only thing we have to fear, is fear itself' is very clear, and quite appropriate, so you might want to try that one if you give it a go.
