[quote=@Vandy]Lex had always hated Superman because he is the one man in Metropolis more powerful than him. Sure in the beginning he would have tried to manipulate him but now we're four years in. Plus if Lex built the Justice League he sure doesn't want Supes over shadowing him on his own super team. Lex is incapable of being second place to an unhealthy and obsessive degree. Superman is the one person he really thinks overshadows him. 

If the invitation comes from Cap that'd be fine but Lex certainly wouldn't be happy about it. Lex has been willing to work with Superman only in extreme circumstances and is on the Justice league in the comics right now so he can undermine Superman's own team. He doesn't want that to happen to him.[/quote]

Yes, and Superman's invitation into the Justice League was years ago. Lex creates the Justice League because he wants to control Superman. When Clark says no, Lex spends millions unearthing superheroes of his own, finding and unthawing Captain America, tracking down Mjolnir that had crashed to Earth, all to spite him by creating the greatest superhero team on Earth. The reason the Justice League even exists in this universe was so that Lex could have Clark under his thumb and when Clark refused Lex made sure it was even bigger and more beloved than Superman - in the current climate at least.

Trust me, I've thought this through.