Who would win strength wise? No prep and this is a random encounter and both are at their peak in strength!
if by peak strength you mean grundy's strongest form which to my recollection was chaos grundy who was giving superman a beat down then i think he has a chance.
Wasnt that in the cartoon series? And Superman in the comics is alot more powerful than the cartoon, but for more on Apocalypse feats you can go to my Despero & Superman Vs Thanos & Apocalypse thread=)