What if Vegeta had not gone on that enraged rampage after Cell killed his son and Gohan actually fought Super Perfect Cell [SSJ2] one-on-one and Gohan wasn't hit with that powerful blast trying to save Vegeta. Both of them not holding back...
1. Both of which seemed confident in their own power that they could win against eachother
2. Cell was able to break SSJ2 Gohan's arm rendering it useless. Cell did this feat with one single blast, although it's hard to tell what attack he used, maybe Special Beam Cannon or just a maximum powered Ki blast or whatnot. This shows that breaking Gohan's arm with one single blast shows that Cell after he had returned to Earth as a supposed possible Super Saiyan 2 [i believe to be SSJ2 at least] was at least very close to Gohan SSJ2's strength, otherwise Gohan would not have been so badly damaged as he was.
3. After which Cell fired a Kamehameha wave against an injured Gohan SSJ2, whom I believe was mostly injured emotionally as he lost most if not all faith in his own ability to save the world until Goku talked to him and convinced him to do the Kamehameha wave of which I believe was the same power as a normal Kamehameha wave with both hands would be. After all why would breaking one arm cause his power level to drought to half it was original, isn't that a bit of a drastic drop in his power level for just a damaged or broken arm? Anyway, he was continually smirking and overpowering Gohan constantly with the Super Kamehameha wave until distracted by Vegeta's blast which gave Gohan the chance to fire the Super Kamehameha wave while Cell was distracted and engulfed in Gohan's Kamehameha and destroyed.
So this being said, who would win in an all out brawl and who his really more superior if they were to be compared. Cell has regeneration on his side though, and every near-fatal/fatal injury he recovers from making him far stronger so I believe it could go either way between the two.