Quake III is one of the better 4-player games on the Dreamcast , and easily the top FPS title for the console
The gameplay is pretty straightforward; Quake III revolves around multiplayer Deathmatch games and its spin-offs like CTF. The single-player mode will place you in numerous Deathmatch games against AI-controlled bots, as you progress through the matches you'll eventually come to a "boss" fight which is essentially a duel between you and one bot that seems to be better than the previous ones. While the bots prove to be a challenge for the first little while, eventually you will be able to take care of them without much problem. The multiplayer mode is where this game shines; here you can setup splitscreen matches with up to four players, and if you are short of human players you can have bots fill the last spot(s), providing hours of fun. One complaint I do have is that the limit of players in any multiplayer game is four, and this includes the online mode; I feel that this game would've been better if it had compatibilty with the Dreamcast VS cable so you can link up two consoles and allow for up to eight players, or four players with keyboard+mouse set-ups.
The Dreamcast controller actually does a pretty good job of handling this FPS; it'll be a bit odd getting used to it at first (I use a south-paw style, face buttons to move/strafe and the stick to freelook), but once you get the hang of it you'll do fine. Obviously, the keyboard and mouse peripherals will allow for the optimal experience when playing higher difficulty bots or online, and if you have an extra set you can still duel your friends on one TV. Now I've mentioned the online mode a lot, and that's because Quake III is one of the few 'online-forever' games on the Dreamcast, so if you want to dust off that modem (or hunt down a Broadband adaptor, but that will put a good dent in your wallet); you'll be happy to know that there are still a few dozen servers up and running (check out Onlineconsoles.com in particular). However, you don't have to go online to find competition as long as you have a few friends for the full Quake III experience.
The graphics on the Dreamcast are pretty close to the PC; some of the original maps were scaled down a tad to fit on the disc, and the textures are simplified on most maps, but it's not a huge distraction. The gameplay maintains a smooth framerate of around 30-35 frames per second for a majority of the game; the larger maps do suffer a bit of slowdown, notably the space maps so you may want to avoid playing those ones too much. The Dreamcast version offers a number of maps exclusive to that port, and I found that many of them were really well done and are fitting on the Dreamcast. I did find that the more human players you have playing the less maps you have access to for your games, and I find that can really limit the overall experience of the multiplayer.
The Dreamcast port also received an original soundtrack to go with its exclusive maps. Most of the pieces are comprised of various rock and metal genres, but they are very fitting with the nature of Quake III; do you think people want to listen to light jazz while they're gibbing opponents with a railgun?...exactly. This is just kind of music that pumps adrenaline into your veins and pushes you farther to get that gauntlet kill or steal a BFG away from a nearby opponent.
Today Quake III Arena on the Dreamcast is one of the more common games for the console, usually costing $10 or less for a complete copy. It is one of the better four-player games in the Dreamcast library, and easily the top first-person shooter game on the system. If you're looking for a good budget game that you can get literally endless hours of multiplayer goodness out of, then look no further than Quake III Arena. The exclusive maps and soundtrack on this version make more than just a direct port of a PC shooter, and considering how inexpensive it is, Quake III is well worth a purchase for your Dreamcast.