Do you think any playable characters currently available don't deserve their spot and think another should have gotten in instead of them? I do.
Personally I think Elektra and Squirrel Girl and Black Cat don't deserve their spot compared to other heroes.
Elektra and Black Cat just fit the same niche too much. We already have more unique Ninja-esque stealth assassins such as Psylocke, Black Widow, and Kitty. Squirrel Girl is definitely unique but I hardly think popular enough to beat some of the current most wanted.
Not so say I don't enjoy playing these heroes. I enjoyed Elektra a lot even though I am not a fan of her character. I just believe there were other heroes who deserved it more.