Communicating with USB gamepad or COM-PORT gamepad (Arduino UNo)

Hello guys,
I have question: Is there any way to connect my USB gamepad to Arduino Uno (5V to 5V, Gnd to Gnd, D+ to ??, D- to ??), which protocol can I use? The same question is about COM-PORT gamepad (RS-232). I don't know much about how these ports works, so, please, can you explain me how to connect them?
Do I need any special convertors, or I can go directly?

Thank you,
WiggPerson.