1.) If you could write a story or see two heros have a comic series where they fight or team up who would they be and why. For example i would love to see a Batman/Green Arrow team up or VS they are similar and yet very different which makes me want to see it, billionaires with different attitudes that use gadgets. one very serious the other very comedic. seems like it would be interesting.
The idea of speculating on which of two superheroes would win in a fight has never appealed to me. The truth is that depending on the story's needs, any hero can be written to defeat any other. I've also been more partial to seeing someone defeat their enemy by being clever more so than beating each other with their fists. Again, this would all come done to the needs of a story, so I can't say that there are any two characters that I'd like to pit against each other in a fight scene.
Again with team ups, what you're saying is the essence of what you want to do with one. If you are working with one character, such as Batman in your example and want to bring out certain aspects of his character in a story, playing him off of a character that shares some of his traits but contrasts wildly in other ways, such as Green Arrow, is a great way to go about that. For me this still comes down to the needs of a story, so it would all depend on my writing a specific character in order to determine who I would bring in to pair them up with. I don't have any particular characters in mind that I would love to put together as a duo.
I know my response is probably disappointing, but it's honest and comes from my own personal approach to comics.