Excellent game that's under appreciated.
That's because it's a brilliant game that almost anyone who loves first person shooters and multiplayer can pick up and play.
The class system in BF2142 is just perfect, unlike BF2 where there were a few too many classes and you always felt that each class didn't have enough abilities, forcing you to constantly switch between them. Well, in BF2142 there's only 4 classes and in my opinion, it's just right.
The only downside to this game, i believe is the slightly higher than average PC specs you'll need to play in populated servers with more than 48 players. Once you get into Titan mode with lots of action going on, you'll experience huge amounts of lag unless you've got a brilliant dual-core processor i guess.
Other than that, there's hardly anything to dislike about BF2142. It's better than CoD4. CoD4 doesn't have any vehicles, BF2142 does. If you want to play in more infantry - focused maps, the BF2142 can cater for your needs.
Although based on the battlefield 2 engine, the graphics look decent enough on BF2142 and you can get away with mostly medium settings to be satisfied with the visuals. Although there aren't as many servers as there are for BF2, which as over 700 populated servers most of the time. BF2142 still has enough populated servers for you to enjoy any map you choose. (over 200 populated servers i usually find with little low lag, i live in the UK).
The sounds are awesome. The sci-fi theme is beautiful. BF2142 is definitely worth its price now (£20 less than $35)