>>102864279>why would he cheat on MJ after all the trouble they went through to repair their marriageBecause it's a long standing (read: stupid) subplot of him still being in love with Gwen and MJ being his second choice, to the point that when he's out of it and says 'I love you' while looking at MJ, he's seeing Gwen - and it's also insinuated MJ KNOWS this, and is at peace with it.
Earth X took this to an absolutely insulting level by insinuating he wished that he'd had a family with Gwen instead of MJ, and that he would have rather had a son with her instead of Mayday. It's fucking shit.
To answer your question a bit more clearly though, I'd cite guilt on MJ's part as well as Peter's extreme attraction to Sarah, and her attraction to him.
Keep in mind MJ knew what Gwen did and never told Peter, and add to that while she was off in Cali he was at a very low point in his life without her, wasting away, and she refused to come back to him. So, when Peter goes off to France or whatever with Sarah, she doesn't say a thing.
>>102864602Stormin' Norman and Peter being buddies when not on the job like the sheep dog and Wile. E. Coyote is always my favorite thing.