I'd have to say that you're wrong!
From you perspective, you look at things that USE the features of DX 8... not just REQUIRE DX8. THere is a difference. I bet you can find games that come out now that are 2D that actually require DX8... but there's no point to it(THere is a point to it as it is, but I expect because it's the latest standard and there's possibly lots of bugs Microsoft fixed between DX7 and DX8, which helps run games better... possibly), since there's no pushing the 3D features of DX8. HOwever, DX 8 offers features iteslf beyond just Pixel Shaders, that was first showcased in Aquanox(which was possibly the first game to actually USE these features Of Direct X).
MErely the requirement of DX 8, doesn't mean you take advantage of it. So in part, Mechwarrior 4 could require DX8, even if it doesn't use many of its newer features. I can guarentee it won't run under Directx 7(as no game requiring DX8 probably wouldn't)!
So, if you're point is that Aquanox is the first game requireing DX8, you're wrong.
BTW, it's probably not too sporting of you to take your argument outside of the forum you're on. Perhaps you could give a link to the argument, so I can get more of a perspective on this? I'd rather answer a question like this in your own forum so that you don't just ignore my answer(not saying you will, but I don't know you, and it happens alot, so don't take it as an offense) and take someone else's who agrees with you, as that's merely a one-sided belief, ignoring those who don't agree.