I bow down to the brilliance of X-Com, because they told their story in a very abstract fashion. You need those events, otherwise it's just a tactical game in superhero clothing. You do get to choose which heroes you take on each mission, however, and that's where the game's strategy elements start to kick in. You can win each mission with nearly any character, but the way that you approach any given mission will be different depending on which characters you elect to bring. That's a page straight out of the System Shock 2 guide to game design, and Levine confirms that this is one of Irrational's guiding principles.
Some games have a lot of branching, a lot of choices there.
I'd rather give the person a really interesting problem and a really broad range of tools with which to approach it, and let them figure it out. Sometimes the game might limit your choices with additional complications. Some characters may not get along with other characters, and could refuse to go on missions together. Sometimes the game might present you with two missions that take place at the same time, and any character that you send on one mission won't be available for the other. Apparently life is never easy, even for superheroes.