>>1
What does it involve? Anyone care to give some insight other than saying reverse engineering?
Sure. It depends on a case by case basis. If you want to do it, you need to know a couple of things:
1) Your platform: CPU's instruction set(assembly) and architecture, your OS' internals and documented APIs, and many platform specific tools
2) Knowledge of how compilers work. For example, how does a C compiler transform some statement into x86 assembly. In more advanced cases, you might have to write compilers/decompilers yourself.
3) Common tools for a platform. For Windows that would mean OllyDBG, IDA Pro, SoftICE/Syser, a good hex editor (not mentioning any to avoid flame wars), and more specific tools such as import/export/reloc recovery tools.
4) Understanding of how your protection works. This is usually gained by using (3)+ maybe custom tools you wrote and knowledge in (1) and (2). Experience helps, otherwise you will gain it here.
Also are bfbc2 and mw2 more difficult to crack. Is it because of propitiatory servers?
I did a quick google search and it seems both of those games are cracked. One of them featured a high-end protection which is rather difficult. RCE is a general skillset, you can use it for a lot of things(such as malware reversing, unpacking, general patching/cracking, protocol and file format reverse engineering and many more, functionality reverse engineering). Game cracking usually means high-end protection unpacking and maybe file format+network protocol reverse engineering. I don't know what you mean by ``propitiatory servers'', but if you mean proprietary servers with an unknown protocol, then I doubt that is the case for those games, but it is the case for those that want to make MMO emulators. I should mention that one of the protections used on that game has a paper published by some cracking ezine, so if you google for the right terms, you might find it.
Will bfbc2 ever be cracked?
I'm talking about multiplayer here in general.
It is already cracked, but there's no multiplayer server emulator. If you want it, learn to reverse, understand the protocol and code your own game server. This may be a few month(s) to a year (or more) worth of effort. It's usually a job involving documenting packet structures and reverse engineering encryptions. It's just a tedious job, but rarely too hard.
If you don't have the patience to do it, maybe you should just buy the game?