Witcher 3 is a good one, it's probably one of the best rpg ever made. However, you have to be ready to play the game for months because thats how long it takes to finish the game.
What about the Dishonored series? They're not too similar to Assassin's Creed, but there are gameplay aspects that overlap. The first one was good at least. Other than that, Rick_the_prince's The Witcher recommendation is great.
Gotta recommend the Metal Gear series with V being probably the most accessible though it may be a bit confusing at first on brushing up with thte story