They're referred to as "A-list," but what does that mean, really? That they get paid top dollar? That they can "open a movie"? I actually see it as a weightiness. Some actors are heavy enough to hold down the big screen and some . . . aren't.
George Clooney is, in my mind, probably the Pet Rock Major of the cinema. That man pins the screen no matter what he's doing. Tom Cruise is up there, too. I'm no big fan of Cruise, but he has weight on the screen, and that's evident even in his early work. These are actors who don't need someone else on with them in order to hold a viewer's interest.
Think of the movie screen as a piece of paper left outside. A big enough rock like Clooney or Cruise can hold it down without any trouble. No breeze will blow that paper away. But some actors are smaller, more like pebbles. They need a couple helper rocks to keep the paper where it belongs.
I won't name names. But I will say that pebbles don't often become larger rocks. You kind of are or aren't a boulder. (A boulder, on the other hand, can be reduced to pebbles should the career fall apart.)
There's nothing wrong with being a pebble. Embrace who you are and work with those limitations. And, though there's talk of this being the golden age of television and television being as good or better than film, let's think of the small screen as a smaller sheet of paper. One a pebble might easily hold down without any trouble.
Many people might find this offensive. It's not meant to be. "You're telling me not to aim higher! You're trying to limit me!" I'm only suggesting you stay in your weight class. I'm practical that way.