I don't know which one came first. Luxor or Zuma... but they're essentially the same game with a slightly different theme. Zuma focuses on an inca/aztec style while Luxor focuses on ancient Egypt.
They're not 100% clones of each other, and neither one was terribly original to begin with. Basically, a stream of colored balls come rolling along a path and you have to launch other colored balls so that when 3 or more of the same color are side by side, they disappear.
Zuma occasionally makes a ball glow to signify that it contains a powerup, and luxor makes any 3 consecutive matches give a random power up. Some of the power ups are very much the same (notably the one that gives you a laser sight to show you where the ball will wind up) and some are way different, such as the dagger powerup which allows you to eliminate single balls with each shot.
It's fun enough to play for 10-30 minutes at a time but after that it starts wearing thin. There just isn't enough progression through the game to make it feel like you're doing anything other than clearing a level (set number of waves? Predermined score? I have no idea).
I think the edge in this case goes to Zuma Deluxe by PopCap. It just has more character to it and some occasional humor. This game is much more dry by comparison. They're both still fun (in small doses) though.