If you like OUAT for... Twisty plots, huge cast, flashbacks, Emilie de Ravin...
Then you might also like: Lost
Why: Before creating OUAT, Eddy Kitsis and Adam Horowitz honed their skills as writers on Lost, and the shows share a lot of traits in common. Sprawling casts whose characters are fleshed out in flashbacks, serialized mysteries, jaw-dropping twists, epic romance (sorry OUAT, but even the Charmings can't touch Desmond and Penny)... Lost has it all in spades (plus, Emilie de Ravin!). If you've never watched it, now's the time. The journey is worth it, even if you end up hating the ending.