While we're battering down the hatches on the east coast for the upcoming mega hurricane, I've been putting the finishing touches on an upcoming Sega project which should be announced shortly. In the meantime, you'll probably be seeing a few blog posts detailing some of the more obscure things I've dug up.
I hadn't previously played much with the Yu Suzuki Game Works Vol. 1 disc - this release was a book that came with a Dreamcast GD-ROM including many of his games, and I'd never bothered with it because most of the included games were already included in Shenmue. In updating the article, various places pointed out that the car model had changed slightly in these versions, from a Ferrari F40 to something that resembled a Testarossa, so I decided to grab some comparison pictures in an emulator.
What I also found out is that it runs in a higher resolution than the arcade game, though it's hard to really see the difference. But, it's noticeable in the below screenshots:
I'm not sure if it's an issue with the emulator or the original software, but the colors are darker in the Dreamcast version. I adjusted the brightness to more closely resemble the arcade version, though you can still see the darker road. The shadows don't work right in the emulator either, seeing how they're just pink blobs randomly strewn about.
The most important thing to notice is that the signs in the starting line are actually legible. What's more, a few of them even changed slightly - that one in the lower-right corner of the arcade version has an OutRun logo, but it's been changed to a cat in the Dreamcast one. There's also a sign that says Treasure in the Dreamcast version, and while the arcade one is illegible, it seems to say something different.
The sprites still look low-res in general, so it's probably no more than the artists slightly touching up sprites here and there, since the game is running at 640x480 rather than 320x224.
You can pick up other details too, like the trees looking slightly less jagged, and so forth. I think everyone's been under the impression that these ports ran the game with the original graphics and then just applied a smear filter when running at a high resolution. I think that's only half true - they may have applied some filters (rather than nearest neighbor) when individually resizing the sprites, but it's also clear that they retouched and redrew most of them, to fill out the detail and reduce the blurriness that such techniques usually suggest.
I'm not really clear about the other games on the disc - Power Drift and Hang On seem identical to their arcade versions, and After Burner II and Space Harrier don't function on the emulator, so OutRun may be the only one with any real alterations.