Do you think that more games that are on multiple platforms should have online for all platforms rather than seperate online for each platform. For ex I have CoD 4 for the 360 while my one friend has it for pc and my other has it for ps3. I don't want to buy the game again for my pc or ps3 but want to play with all my friends online. SO my question is Should more games that are cross platform and have online be able to play online with any console.

will not happen - esp. with xbox live competing against the free PS network

 Well then game devs should just use their own servers rather than microsofts and sony's. Yes it would be expensive but it would also get more people to buy the game. 

^they could not compete with live and PS network

 I'm not saying that they would have to compete. It would be like how ebgames used their own servers for medal of honor heroes 2. It has nothing to do with competition when microsoft and sony aren't using thier servers for a game. 

well....i think the devs. simply won't put that much effort into it for little if any return

 Its not a matter of effort rather of money for the servers. I would also think it would get more people who own one console but all of their friends own another and have that game buy the game just so they could play online. It would increase game sales.