lol...shoryukens are a breeze. In fact, I do them by accident waaay too much. In world tour, the reason for doing better is because that mode is made for you to build up your fighter. The challenges come in when you have to defeat 3 opponents one after another. However, even those aren't that hard. I find that 100 kumite is also pretty easy. I started losing out of sheer boredom.
Supaman, for you I would recommend lowering the difficulty level and spend quite some time training for the harder fights. Practice combos which make you feel comfortable. For example, I don't like to do distance fighting (hadoukens and the spinning kicks). I'd much rather jump in with a kick followed by 2 mid kicks then a fireball or spinning kick. If they are in the corner you can follow with the Shoryuken. This all takes time, and not all fighters are the same. For example, Guile works better when you plan your attacks. For example, jump in with a kick/punch continue to hold down. Do a Fierce Kick while holding down. Then do his somersault kick. These are all basic and very simple combos. Try it out.