It is a very rare occurrence when two completely unrelated companies in the videogame industry do a joint project to deliver something nice to gamers. Japanese games have done some projects like Cross Edge, but they usually don't live the expectation. They seem to be more fan service than a dedicated project. Other times they deliver something really good, like Street Fighter X Tekken.
Of course we can't expect them do be all great friends and in disposition to do this, since they are business and they are after the same customers. they are after the same money and so it makes sense they will try to out do one another. But sometimes they do nice things, like a homage to another company great game in form of a cameo or piece of equipment.
But I think they should sit down and mash up their franchises more. Not only this can become a great game and best seller, but collaboration can improve many of the involved companies. They can share ideas and concepts and maybe come up with something great from it. And keeping good relations between each other and keeping business just business is also wise and good.
To the gamer, it means more games with their favorite characters in it. It can become a nice topic of conversation and if the game turns out great, it opens the doors for more crossover content between companies, which cannot be a bad thing.
Of course, as long as it is done right. Doing a bad game and selling it using only the power of the names involved in the project is not a good thing. Quick money grabs will sour the expectations on those projects and make gamers wary of any attempt in cross over. But when done right, we can have all those dreams of 'who would won a fight' and 'imagine a game with those two on it' come true.
So, I am all for more crossovers. Just do them right, game industry.