First of all lets get to the point of the matter. All cross-overs are subject to interpentation. So lets just have some fun here.
In the battle of the JLA vs. the Avengers, I Fell that it would go like this:
Superman and Thor would pair off and size each other up at the start.
She-Hulk goes after Wonder Woman and begins to try to use here STR to her advantage. Not knowing that
Wonder Woman is her equal in STR, and unaware that she is able to parry all the blows that the green skinned wonder can throw. Also all the blows that Wonder Woman lands on She-Hulk is absorbed by her natural body armour. This ends up just being a parry vs. knockback battle, destroying near 7 city blocks in the process.
The Martian Manhunter and the Vision takes turn trying to hit each other, all the time missing because one or the other goes desolid at the last minute. Martian Manhunter trys to use his mental powers but cant because the Vision is a machine.
Batman and Captain America will go toe-to-toe, all the time trying to figure out what the weakness of the other is.
Flash and Quicksilver take off running at superspeed and with both wanting to prove that he is the fastest, we never see them again (except in passing).
Firestorm goes after Iron Man, and Iron Man hits him with several good hits. This gets the better of Firestorm and just before he goes down for the count, he turns Iron Man's suit into a giant paperwieght. Both men are down for the count.
Here comes the Flash and Quicksilver.
Superman and Thor go at it and Superman gets tired of being hit by Thor's hammer. Superman uses his superspeed and puts some distance between him and Thor. Thor sees this as a sign of weakness nad throws his mighty hammer at Superman. Superman surprises Thor by catching the hammer and holding it, preventing it from returning to Thor. As only a person of great virtue can pick up let alone hold the mighty hammer, Thor quicky comes to the conclusion that this battle was caused by some evil force of great power. He approached Superman in peace and they begin to talk.
Look out for the Flash and Quicksilver
Batman and Captain America having come to the same conclusion 10 minutes eariler wonder what took them so long.
Superman goes to calm down Wonder Woman while Thor does the same for She-Hulk. Vision and the Martain Manhunter stop trying to hurt each other and also begin to talk.
Both teams revive their fallen members and Firestorm returns Iron Man suits back to working condition.
Flash and Quicksilver just passed by. Did anybody see them?
All the remaining menbers talk it over and realize theat this whole battle must have been cause by none other than........
Loki and Lex Luther. So begins another cross-over as our favorite heroes go after a couple of villians.
There goes the 2 speedsters again.............