Serious question: was Linux able to play any kind of game in 1998? Linux releases are a little more fluid so there aren't as many big moments, but I'd imagine it was a hell of a lot less capable in '98.
There was a fair amount of AAA gaming support around that timeframe (say 1996-2000). Almost a golden age. Games based on the Quake engine were the most obvious example. Besides them, Loki ported maybe 20 games over to Linux. The ones I still have CDs around for somewhere are Railroad Tycoon 2, Heroes of Might and Magic 3 and Myth 2.
A friend bought a Quake III for Linux tin box from the discount bin because they had put a sticker on it saying it also worked for Windows.
Inside was a instruction sheet informing Linux users how they could use CVS to pull and compile 3D support, depending on their distribution. I thought it was rather funny that someone felt they could market a game to people who were compiling their own operating system. I guess that's why it was in the discount bin.
I am pretty sure that the Quake 3 demo was released for Linux first and my memory is that this was an intentional move by Carmack to promote Linux .
1. Wikipedia lists the release dates for the full game, which were in Dec 1999 for both Windows and Linux (windows a few weeks earlier). I don't recall exactly when the demo came out, but I think it was sometime in the winter of 1999.
The Linux installation got easier, but from a Desktop user's point of view features did not change much since '98 as far as I remember. Sure there is now (serious) support for all the new fancy Hardware like Webcam or SMP Processors. (I'm having doubts whether it's correct to say that Audio improved^^) But OpenGL was always there. Actually SDL was very popular during that time (SDL = OpenGL + X ~ Direct X) Interesting, I just read that it was actually Loki who developed it in '99 -- all their games were SDL based.
Otherwise you're right, setting up Linux Gaming computers with working OpenGL Hardware Acceleration was painful, especially for us poor people who could not afford the most expensive OpenGL Hardware. ;) On the other hand I think audio was easier to setup :P
In those days, Voodoo cards were all the rage. There was a binary Glide library available for Linux; Mesa could link against it and give you full OpenGL (with some limitations, such as texture size) support. GLQuake and Quake 2 ran; and non-3D games could certainly have been made to run had the developers cared to. (I coaxed StarCraft into running with Wine, but it didn't have IPX support so no LAN play.) About a year later, the Quake 3 demo and eventually Quake 3 itself ran under Linux.