Gena Rowlands, even if you never saw the original. The problem isn't with Stone, who seems like she'd be perfect for this role, but fits into it awkwardly at times.
Stone can be a powerful actor when working with the right material.
But the movie doesn't know what it wants to be. In fact, her scenes with kid actor Jean-Luke Figueroa are the best, especially the really long shots where the camera doesn't blink. You believe these two are bonding, and never sure if the dialogue is improvised or not. Stone's Gloria is all blustery and frantic, even when she's seemingly in charge of a situation, where Gena Rowlands wore her angst more on the inside. It's the whole mob plot that fails miserably.