the query you provided will show you all registry values, not just startup parameters. you would need to add where clause to return startup parameters only.

SELECT value_name,value_data FROM sys.dm_server_registry

WHERE registry_key = 'HKLM\Software\Microsoft\Microsoft SQL Server\MSSQL11.EXPRESS\MSSQLServer\Parameters'

you can run my provided code on 2008 R2 and compare it to the results from sys.dm_server_registry. it should be returning all the startup parameters.