I'm sorry but I just couldn't resist but instead of taking on the Avengers, what if the following versions of Superman were up against Loki's army; this would also include Loki himself.
So I have two scenarios that will assess how each Superman version does
Scenario 1: Superman(Reeve) vs Loki's army
Scenario 2: Superman(Routh) vs Loki's army
If Superman has too much of an advantage in either case, I'll allow the foot soldiers to each carry a shard of Kryptonite. If either Superman is somehow outmatched then he can gain the aid of one Avenger.
Scenario 1: Superman wins he had just too many crazy feats.
Scenario 2: I could see Superman possibly losing. He was durable as hell against bullets but so was every other high end character in the Avengers and the alien lasers were still hurting them. They may effect him if they do it could be a long day for Superman.
Superman's going to have to resolve to kill the Aliens and the giant creature carriers though; he can't just keep conking them out while they keep coming.
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"I'm not smart so much as I am not dumb." - Harlan Ellison
Aww man...I though there would be more of a fight especially with Routh's Superman. Afterall I did allow the foot soldiers a shard of kryptonite and that should give the Routh version trouble at least right?
Though I think I agree that Reeve's Superman wins in round one.
Based on these feats from Movie Superman vs Nuclear Man..I will still go with Loki and the Gang plus the Thor and Hulk. Supes fighting skills didn't look impressive.
Routh Superman showed more resistance to krytponite than Reeve's did. He managed to lift a small island made in part of the stuff while having a small shard of it still lodged in his body.
Though they're the same Superman. Returns is an alternate Superman 3.
Routh Superman being a deadbeat dad, his palnetary strength and speed would not hurt movie Thor. When Thor got smashed by Hulk numerous times, he never seemed to be injured. I don't think Superman will even dent Thor's hide. He will probably knock him through mountains but Thor just gets up. I believe the Hammer of Thor will decide the winner.
Lifting feats while flying are not feats of strength. Superman is extending the power he uses to fly to the object he is holding. It's strength of will rather than muscle, really.
Look at the fight with Zod, Ursa and Non in Superman II. Standing on the ground, it took a few of them to lift a city bus and throw it at Superman, and they all had identical power to him.
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"I'm not smart so much as I am not dumb." - Harlan Ellison