Its a hard choice, but I'm going with Samurai.

Sure, it was a heavily watered down Shinkenger with extra bad acting, but it was still much better then Megaforce, with its even worse acting, lack of any personality and bland excuse for a plot.

Maybe it helps that I saw Samurai before Shinkenger and was unaware that it was mostly a watered down copy, but Samurai at least had a plot and the characters felt like characters, which is more then I can say about everyone on Megaforce bar Jake.