I'm personally a BF2 fan myself. Especially the underappreciated DCON mod. But it's getting pretty hard to get enough players together for a good match of DCON CTF in BF2.
I bought COD4 a while ago, played a few hours of single player then had it sit on the shelf, for the future.
I saw an Xfire stat that showed 14 million monthly minutes of COD4 play vs 2 million minutes of BF2 in the same period, so I started looking at COD4 for capture the flag mods.
Anyway, if you set the switch to allow it to include MODS in the server listing, you might discover a whole new world of maps that you might enjoy. It's cool how the game downloads them off of the server, then automatically plays them. It was downloading content before every round, so I assume they were all new maps.
I haven't actually played enough to know which maps are stock (the ones you guys are bored of).