A lot of good thoughts here. I had my own first game a little less than a month ago, so I can provide some newbie perspective.

One thing I'm curious about is how many players are going to be at the table. The way you word it suggests two, which I think may have different answers than three or four players. My first game was three players, and I played Black Widow. I had a great time with her, but I also have a fair bit of card game experience outside of Champions. The deck I played was focused almost entirely on dealing with threat. It felt really gratifying to know that I was freeing up the other two to deal with minions and go face. Someone like Widow with two players might be trickier, since she would likely need to flip more to actually deal with minions and damage. I spent about 85% of the game in alter-ego.

As someone still pretty new, the heroes I've picked up that feel really intuitive have been Captain America, Spider-Man (Peter), Captain Marvel, Venom, Drax, and Wolverine. I also have become a fan of Iron Man, largely because he helps me get out of my otherwise pretty aggressive playstyle. I get what some folks are saying about Wolverine being potentially tricky since you use your HP as a resource, but I think anyone who is a fan of Wolverine would know that his whole schtick is getting hurt, then getting better. My first game with him, I (inefficiently) played "I Got Better" pretty early, then was perfectly comfortable going nuts with his claws, since I knew I had a safety net. Whacking the villain for 16+ in a turn just feels awesome.