First a little 'get-your-facts-straight' nitpicking...
Originally posted by Starhawk
Also Thanos had other Gems at that time and didn't beat the power gem through brute force.
Thanos only had the Soul Gem at the time he fought Champion. But like you said, he didn't beat him through brute force...he outsmarted him.
Originally posted by Wally West
Thor beat Warlock and Strange together with the power gem,
Thor didn't have the Power Gem when he first beat Surfer and Warlock together...that was sheer bloodlust under his own power.
My opinion on the topic of Drax vs. Superman: I can agree with Starhawk to a point...that if you understand what the Power Gem is and the type of power it grants a wielder, then current Drax would, without question, be far more effective with it today than he ever was as dumb Drax.
There is also no way to measure whether or not he would be a threat to PC Superman without any feats. Guesswork can only take you so far and holds little water in the face of actual feats.
Current Drax would be extremely dangerous and powerful with the Power Gem, but able to do some of the things PC Superman did? Highly unlikely. You need to turn your hyperbole filter up a little if you're relying on the statement of 'it gives him complete control over power'. Sounds a lot like Apocalypse and his ability to 'grant himself whatever power he chooses'.