Everybody wants somebody to win, especially teams in the prem. I always look at how the results will affect us, if the mancs won and it benefitted our league position (except in extreme circumstances) i would be happy. As has been said, after that different variables come into play, manager, fans, players or the fact they are underdogs.
I follow my hometown club but only occaisionally and tbh i dont really care how they do, fair enough it benefits the city but deep down i dont really care. The only match that puts me on a massive high when we win and a massive downer when we get beat is Liverpool fc.