How many users can log in in same time on windows server 2003 and 2008?

Default only 02 

I mention Limit Number of Connections =3 and selects enabled option. Also I did Restrict Remote Desktop Services users to a single Remote Desktop Services session = DISABLED.Still it's allowing 2 people.

Yes. By Default its two but you can change it through the following wiki.

http://technet.microsoft.com/en-us/library/cc753380.aspx

two users through he Admin Remote console and one user through normal remote