NOTE: United Offensive REQUIRES/NEEDS the original game to be installed to function.
United Offensive takes almost everything great from the original Call of Duty and builds upon it. New larger maps, a campaign as long as a standalone Call of Duty are on offer up-front. Behind these large offerings are smaller but notable additions, such as driveable vehicles and new weapons for each force in the game.
The campaign is slightly shorter than the base games by about 3 missions. The campaign itself is still about as long as, possibly longer than what is offered in Advanced Warfare, a definitely longer than Modern Warfare 2 and 3's single player. The American missions take you across France in large battles for control of towns, fields and ridges in the besieged countryside. The British missions start you in a RAF bombing raid as a plane gunner before switching to covert missions for the SAS. The Russian missions follow a small unit as they fight their way to Kharkov to liberate it from Nazi invaders. The campaign features the usual Call of Duty missions where you do slightly different things from the usual infantry boot work, such as drive-by turret sections, the RAF section and the Soviet tank mission which is similar to the tank mission in the originals Soviet campaign. Overall, the campaign is well made, the variety of missions under such a tight gameplay build is something that this and the original have that the modern games lacks.
This helps the gameplay factors. The lack of regenerating health means that you never feel like a super-soldier. You will probably want squad members to take point to avoid getting your face shot off by an unexpected MG42 gunner. The levels are built for PC players and the maps are built for vehicle traversing as well as on-foot movement, so a scale not present in later instalments is clear.
Visually, the game has aged. Animation looks hilarious sometimes, the faces look really bad. The environments look a little middy, but are large and grand. On higher settings (which I think a toaster can do now), the environments are more than passable. Forcing Anisotropic Filtering cleans up a lot of the problems with the games textures. Although the game is not beautiful, it is passable and the visuals never interfere with the game itself.
Audio-wise, just like the original, the soundtrack is brilliant and memorable, with the OST being pretty much identical to the original. The gun sound effects are decent, again being re-used from the original. The voice acting is hilarious sometimes, with the fake Russian accents being the most memorable. The German voice work is brilliant as well, with a few shouty lines being spammed across the whole campaign (This is re-used from the original). As with all the main instalments, the amount of chatter on the fields, screaming from soldiers to move and take covers enough to keep the player in the game.
Multiplayer-wise, if you can get on, people still play it. The maps are well-done. The use of mounted guns and vehicles means that the game is played differently from later games in the series. The maps are much larger than what is offered in later games, changing how multiplayer is played as they are far more open due to the different methods of play. There are some problems with weapon balancing however which is present in both this and the original game.
My only actual complaint would be within the campaign. Sometimes some objectives don't trigger themselves properly (well, it happened twice to me) and although the campaign is solid across the board, the Russian campaign could not quite beat the atmosphere shown in the original Call of Duty game during the Battle for Stalingrad, which is my personal highlight for the series. Despite this, the expansion pack goes above what many other games in the series attempt and is in my opinion, the best of the series. Any fan of the genre should definitely get it and any fan of the new ones should get this to see how Call of Duty should be done.
+Excellent Multiplayer Design
+Many Great smaller additions
-Some bad voice Acting
-Some bugs in campaign progression
In Short: The best of the series.