The Energon Pub

Hulk easily.

Might as well get it out of the way now.

"HULK SMASH!"

But yea, Hulk would turn Megatron into a tin can.

Hulk would grab onto his chest panels and shoulders and anything else he could get his hands on, and just tear EVERYTHING peice by agonizing peice. Megatron would be nothing but a pile of metal flakes. Seriously, with the way the bots from the movies fall apart, all hulk would need to do is flick him in the right area and he'd dis-assemble or something.

Hulk.

Unfortunately, Hulk is one of those characters who's power level is variant depending on his customer popularity...peaking during the World War Hulk series.
I mean, seriously, him holding a whole PLANET together when it was splitting apart? A tad bit redonkulous IMO. Marvel "leveled" him up to the point where there are no real possible challenges for him as a character...I prefered the older universe where heroes actually had challenges and had to overcome adversity, otherwise what point is there in being a "hero" if everything comes so easily? Things like bravery, honor, and the "persevere through adversity" thing that used to define WHAT a hero was kind of loses all value when any hero can solve a problem with as much effort as it takes a normal person to blink their eyes.

Its the same thing that ruined the DBZ universe...instead of coming up with "real" challenges, they just made the villains more powerful...and as a result leveled up their heros to overcome them...eventually resulting in a Super Sayan level 378 with mile-long golden hair who took 17 episodes to "power up" their ultimate attack.

The only realistic comparison would be a Megs versus Lou Ferrigno era Hulk...not a complete blowout but Hulk would actually have to dive, duck, dip, dodge and dive to avoid being pulverized so he could have a chance at winning.

With one twitch of an eyebrow, Hulk wins.