Street Fighter was always more fun to play than Mortal Kombat because the characters feel more diverse and the animation was smoother. Mortal Kombat has its moments, but the shock factor of its gore got it more attention than the actual gameplay (nowadays it is a very competent game though, I just disliked the first one).
street fighter because of the more different characters
I disagree. I truly believe that MK has way more characters than street fighter. Ever played MK Armageddon? Well that one has all the characters ever on MK.. and new ones. It totals to 62/63 characters. (The Wii version has Khameleon, the female Chameleon). I don't really know how many Street Fighter has.. If they have more then I'm wrong. Sorry.