Although it's old, it's a great game with addicting multi-player and with so many modded servers, the fun will never die
The simplicity gives so many opportunities for enjoyment. It's like Halo, it's replay value is very high, and after playing it hundreds of times, it is still amusing.
The first Call of Duty + United Offensive brought new features to the gaming experience such as drivable Tanks and Jeeps, operable Turrets and Cannons, and gameplay modes such as Search and Destroy, Headquarters, and Bases that really powers UO's fun.
Plus, mods and custom maps add to the fun. It is a bit of a pain when the file sizes are large and download time is long, but they're worth it. Some of the maps I've seen are incredible, and to understand you need to try it yourself.
If you see this game at Best Buy or at some electronics store, and you have some extra money, buy it. Make sure you get the United Offensive expansion pack too, because almost all computers can support it, and it's really worth it's cheap price.