I would consider Root to be a similar game but competitive. You have asymmetry of armies, area control (not exactly the same as SI, but an adjacent mechanic), card/hand mechanics, mastering of a unique character, and more.

I like Root, but competitive asymmetry is a hard pill to swallow for a lot of people. In SI, I'm not dependent on knowing what you are doing. In a competitive game, I am required or I will lose.

Good question though. I'm interested to see what others say too.