I have a basic question.
Is the SQL Server 2008 R2 Developer Edition same as SQL Server 2008 Developer Edition? Why does the Microsoft sites return 2008 pages while browsing when looking for R2 editions?
No, they are different products. Can't answer why your searches would be returning the incorrect info. The developer editions of SQL Server are functionally equivalent to the Enterprise versions, though, if you are looking for specific information.
Here's the US/EN page for SQL 2008 r2 http://www.microsoft.com/sqlserver/2008/en/us/r2.aspx
In Microsoft SQL Server 2008 R2, several components have new or improved features. Other components have not changed since SQL Server 2008. Those components offer features that were new or enhanced in that release.
As the others have stated the SQL 2008 R2 release (any edition) is fundamentally different from SQL 2008. You will note that each have a different version number.