^ I felt that the comic made it amply clear that Thor was not looking for a fight, kept asking for an explanation as to why Gladiator was gunning for him and then outright told him that he had been holding back the entire time right before he turned around and stomped him?
The "have at thee!" and enraged hammer blows right off the bat sort of belie the "didn't want to fight" angle.
The same sort of excuses can easily be made for Gladiator in the later fight, seeing as the two teamed up to save a passenger jet and then immediately after doing so Thor suddenly hit him with a big blast and didn't let up.
At any rate, I don't put much stock in the "I was just holding back, honest" excuse that Thor may as well put on his business card. If his holding back had gotten him killed in that first fight with Gladiator, as it would have if not for the arrival of Tarene and Enchantress, would someone have excused Thor's poor performance in his eulogy?
"We gather here to mourn the passing of Thor, who, rest-assured, only died because he wasn't really trying in that fight."
I usually criticize apologists who break out the "he/she really wasn't trying" card. I find it to be an all-too convenient excuse. But here, that was clearly stated. After all, Gladiator popped up just intent on ending Thor and Thor was bewildered because he himself had not lived through the events of The Reigning where he takes over Earth and had no idea what Gladiator was talking about. Sure, it's Thor's own fault for trying to save civilians from flying bricks and then getting pummeled by a speed-blitz, but he was holding back. It was only after their fight endangered that airplane full of passengers did he totally lose his patience and really go all out:
Excuses are excuses, but facts are facts too. The fight was a bit circumstantial because of those facts. And really, if you want to divide their encounter into rounds as a compromise, then sure, Gladiator won against him in the opening round, but Thor literally clobbered Gladiator in the second round. My two cents.
The other thing to consider is that while it was stated, it was stated by Thor. The biggest egomaniac in comics. Has he ever lost a fight where he didn't come quick with an excuse afterward? "Now that I've tested his mettle..." and so on. I think he even managed to lick his wounds saying something like that in JLA/Avengers.