The thing is - it's THEIR marriage. Whatever you or I would do in the same position is just not relevant. Only the two people involved really know what they need and want. I think Will Smith is a great guy and he is obviously very smart, accomplished and confident. He has made the choice that is best for him and we should respect that.
While I would never condone cheating on your spouse, so I don't respect Jada Pinkett Smith for doing that, at the same time, I don't want to tear her down either. Again, I haven't walked a mile in her shoes.
I sincerely hope the best for both Mr. and Ms. Smith... :)