It wasn't "Normal" Genis... Photon was just as powerful as Insane. Insane just seemed stronger because he used powers he never would have otherwise because of the harm they can cause.
I have to say, as execrable as the Void is as a character, Genis is the most overrated character on this entire forum. His high-end, universe-destroying feats are all PIS and totally inconsistent with the power-levels displayed in his fights, in which he is consistently shown to be a high-end high-herald. His BFR capabilities are some of the best in comics, admittedly, but Void's combat feats are simply superior. Void wins unless Genis can BFR him.
Things like disintegrate Loki w/ Norn stones, ressurrect himself, overpower Molecule Man, rip Ares in half, taking on the avengers/x-men/FF/Doc Strange/Blackbolt simultaneously and have the decisive advantage, taking out Thor like he was nothing (in what if) etc. Genis, by comparison, can go one-on-one with characters like Hyperion, Silver Surfer, King Thor, but never with the kind of superior firepower that Void displays.