Is the alnico classic pickups on a epiphone sg-g400 the same as a seymour duncan alnico pro 2 (used by slash)

They're stock Epiphone pickups, and won't be as good as the Duncans. They'll give you a slightly different tone as well, most likely.
You can hear soundclips of the Alnico Pros on the Seymour Duncan websites. The Epiphone pickups aren't brilliant. They're decent enough, but at times can get a bit muddy and generally lack the nice sounds of some other stock pickups.