In my opinion...YES!!!!!!
If you think any of the Battlefield series are awesome, then you HAVE to get BF2142, it is definately worth it!!
The reasons why it is worth it? Check out the following...
1) The action is incredible (online and off)
2) You have to unlock essential items like grenades, but it makes you want to play more...
3) Titan mode is the funnest way to play in my opinion (but good old conquest is still fine...)
4) You can take advantage of the new age weapons
5) You can track your stats online...
6) It is AWESOME!!!!!
7) The buddy list is a nice feature...
8) It has amazing graphics (even when they are on low...)
9) It is easier to find servers with lots of people on them
10) The gameplay is just fun, awesome, and addicting...

Well, now you have the reasons, so go buy it!!! BF2142 is definately worth the money, even better though if it is on sale...
Also, this just may be a bias on my opinion, but 2142 is better than 2 because people don't play 2142 as much so as a new person, you actually have some sort of a chance...
Well, what are you waiting for? Go buy it!
_DarkStar2119