Well....at first he'd be happy. Only three Super-powered individuals existed on 'Earth Prime'. Himself (teleported from Krypton) , some Alien ***** who just popped up out of nowhere and the Animal Man writer*.
He'd fulfil what he presumes his role to be as 'Superman'. The world would react very differently however to the way that SBP thinks it would. Instead of loving and adoring him a large number of nations will begin studying him and making weapons. Just in case.
America will no doubt be very twitchy with him. After all when you have a technical god who claims to stand for 'Truth Justice and the true American way' you tend to begin watching your enemies just in-case they take offense.
Cults would spring up like anything, watch as Conan 'O Brian and Fox news alternate between theological 'Late Night Talks' comparing (or outright stating) SBP is Jesus or one of many deities.
Unfortunately something WILL go wrong. SBP has severe emotional issues , can't control his strength well and has a very child-like mind. He'll either say something wrong or hurt someone so badly that the entire world will be shocked and disgusted.
Enter the nemesis. As Batman Begins puts it so plainly, escalation.
Earth Prime suddenly gains a 'Superman' , well....we all know who can stop him ? Yes, you thought right. We get a Batman.
And when Prime f*cks up (and he WILL f*ck up, make no mistake) Earth Prime Batman (Most likely a special faction within the military, sort of a combo of Cap and Bats) will be there to take him down.
*For the life of me I can't remember his name.