pg -13 is a relatively new rating, there was no pg-13 (not here anyway) when superman was released... if there was i have no doubt
it would have been pg 13
spiderman has better special effects due to advanced technology (thereby allowing more action), and if i remember correctly clark got the shit beat out of him(when he lost his powers) and yes, there was blood...
superman as a hero doesnt bleed very often, but he did have his ass whupped many a time...
i want to see the new superman movie, i doubt it will be pg...