This is a very good game, and by far the best RTS on consoles. The CommandStick Interface improves vastly upon the old tiberium wars selection screen, and makes selecting what you want very easy.
First off, the campaign is very good in terms of gameplay. You get to do missions varying from shutting down an ion cannon network to activating a cyborg army. I felt like the missions were quite varied and a joy to play (except for the first one, which is way too hard). As for the story, I didn't really know much of what was going on, as the campaign spans over a 20 year period. The difficulty level was very manageable, and is just the way I like it for games: Easy by default, but you can crank up the difficulty if you want. There are also video sequences with real actors before each mission.
In the skirmish mode, you play against computer controlled AI opponents, who have 4 difficulty levels: easy, medium, hard, and brutal. You can also specify what playstyle the computer will use: you can choose from teching up as soon as possible, using fast units to strike unprotected structures, and so forth. One thing I would have liked for this game is the ability to play against the AI with your friends, like you do in StarCraft 2. The units are very well balanced, and the diversity of maps is incredible. CnC3KW adds 6 subfactions to the traditional 3 in tiberium wars, each with their own units, powers, upgrades, etc. . Although the subfactions add a lot of diversity to the game, they also make it confusing at times to tell, say, GDI apart from Steel Talons (unless you look at their vehicles). Unlike the PC version, which automatically adds veterancy, money, and healing crates by default and gives you 40,000 tiberium to start, on the xbox you can change whether you want crates in the game or not, and how much money you start out with.
For the multiplayer, EA has decided to trash the EA servers and account requirement and just use xbox live instead (thank god). This also means that you will have to buy an xbox live gold membership to play online. There are very few players playing this game, for example when I wanted to play matchmaking, it said at the bottom of the screen that there were 45 players playing online. Yes, you read this right. 45 players in the entire world. I think it's probably just because the game is 6 years old and most people have already gotten tired of it and moved on. Finding matches will be hard on this game. However, if you do manage to find a match, though, the computer picks a random map and faction for every player, and everybody automatically is given 10,000 tiberium. I think it was good that they chose the random factions thing for the game, because this way, it is more diverse and players learn to appreciate the strengths and weaknesses of each faction.
There is also an xbox-exclusive game mode called Kane's Challenge, where the enemy has a pre-built base and you have to try to build up and destroy them. There are about 80 challenges that you can play as any faction, but what puts me off about it is the fact that your progress doesn't sync across factions. For example, if you beat the first challenge as GDI, you can't play the second challenge as scrin. So, I constantly find myself replaying missions I've already beaten just because I wanted to play a different faction.
The final game mode is just a tutorial called boot camp, but it is very basic and if you skip it, you get an achievement worth 10 gold.
Overall, I really like this game and it is the best strategy game I've ever played on my xbox. I reccomend it to anyone who likes RTS games.