Dedicated server out of the box. Can't find a server you and your buds like from the server list? Have a spare PC, a decent upload and know what the eff you're doing because you're a nerd who also likes video games? Bam, you can have a server up in less than a day with all the admin controls you could ever need physically in front of you. No paying EA for a server you don't even have complete control over and troubleshooting through nothing but web admin and customer service. It's an nice option for people want their own server without hassle, but it's nothing I'd ever use. There's plenty of decent communities to become part of.
Audio. Aside from the cool but cheesy effects you get BC2 (funny doppler, shell shock) the positioning is superior in BF2. The game also has better channel support (that's pretty bad for a game is made when a lot less people had 5.1 and 7.1) and can handle way more simultaneous channel instances. That's kinda nice in large battles...
Netcode. Everyone knows BF2's wasn't perfect but I'd take it over BC2's any day. Far more consistent, accurate and efficient. Handles more players more easily. Can be modded to handle even more players.
Controls and movement. Some people say everything about the BC2 movement is intentional by design. I question that but even if it was, it's crap compared to BF2's. Not to mention it gets even worse with any kind of lag. It'd be like comparing GRAW to UT, one is delayed, slow and frustrating while the other gives you a much better feeling of control and responsiveness. Any kind of delay is a very clear form of gameplay balance, where in BC2 it is not. It just feels like lag and crummy animations.