Check the stats on Xfire then check the post count in the two respective threads here on BF2/2142.
Then check the Active server count on both games. BF2 wins in All aspects.
Player base, Server population, Mods, Clans, History, Gameplay, Maps Etc etc etc
Then listen to someone who plays, namely Me

for a totally one sided argument as to why you should get BF2 & Spec forces.
To save me Reams of writing about how good BF2 is i will just say, I bought the game for 30 odd quid over two years ago & have logged nearly 2000 hours. I was playing last night & the day before & just about every god damn day since 1 second past 9am on day of release. Still loads of servers populated with other BF2 fans killing each other 24/7 screaming with laughter or crying with rage.
For me a 64 man Infantry only BF2 server is my gaming Heaven
2142 Meh
All that spacey crap, i like real guns me
Played it on release but it's just not my thing. I can quite understand why people play it but i just feel it's a younger generation thing in my case. I don't mean that disrespectfully at all, i just think that the younger dudes seem to like that spacey crap where as an old git like me likes real guns & real bullets.
Think that's about as fair & as short as i can make this post. BF2 for the most people but to be quite honest it'll be down to you. I would strongly advice getting BF2 & hooking up with a few vets. The whole experience of team based play is taken to a new level since IO came out. Steaming around a huge map with a gang of lads chasing down other gangs & shooting the bejesus out of each other BF2 style, slinging in a few teabaggings for good measure endlessly day & night for 10 quid
How ******* cool is that.
*Ends Bias Post*