There was another 3D game by Sega from 1982 called Buck Rogers: Planet of Zoom. It utilized the sprite scaling technique developed by Steve Hanawa for Sega's Turbo which was released the year before. You can see a lot of games branching off from Planet of Zoom -- for one thing, it looks like a chase cam version of Zaxxon in a lot of ways. But even more strikingly, it looks like it has the DNA of what would eventually become Space Harrier just three years later. It's even got a boss ship that reminds me a lot of the refueling plane in After Burner. It was a pretty big hit, getting conversions for most platforms of the era, including the Colecovision, Atari 5200, TI99 and Apple II.
[youtube]http://www.youtube.com/watch?v=PnoEcMbj6FQ[/youtube]
And here's some Sub-Roc 3D footage:
[youtube]http://www.youtube.com/watch?v=VpTAhOp355w[/youtube]
When speaking of the pioneers of 3D gaming, I think it's important to note that while Sega was trailblazing with the stereoscopic technique of synchronizing shuttered lenses to the refresh rate of the monitor, and developing sprite scaling, Atari was innovating in the realm of 3D modeling using vector graphics with games like Battlezone, Red Baron, and perhaps the masterpiece of that era, Star Wars. Two very different approaches to 3D that both formed important foundations for what we have these days. Star Wars also features some of the first digitized voices (although I think the very first might have been in Berzerk by Stern).
[youtube]http://www.youtube.com/watch?v=zSwul6HaGag[/youtube]