I too was going to mention Battlezone. It's still absolutely worth playing, has run fine for me on xp, and with the texture updates still a quite decent looking game these many years later. If a master server were still supported I'd probably still enjoy a strat game now and then
Tribes Vengeance could have been a great game. The single player element was pretty good in itself, but a total lack of enthusiasm by Vivendi in it's release ensured weak sales from the start, and the subsequent failure to support the game with a much needed patch.
The Tribes franchise is unique among "team shooters", most especially because of the use of jetpacks. The learning curve of the games is tad higher than other shooters because of this, but it remains a special niche in the fps genre that has yet to find the mainstream.
The original game has been free for some time, and I recommend trying it to see the potential. Within the Tribes community there is a saying "Once you jetpack, you never go back."
ftp://ftp.sierra.com/pub/sierra/tribes/other/tribes_fullgame.exe