There is no denying the huge scope, ambition, and majesty of Ben-Hur. This is a huge, sweeping epic that helped create the parameters of what makes a 'blockbuster'.
Furthermore, the chariot sequence is one of the most memorable moments in cinematic history -- tightly choreographed, superbly edited, and beautifully directed,
There comes a point, though (it's usually at about the 2-hour mark) where all of this epicness, all of this dazzling spectacle, becomes a bit much.
By this I mean to say that Ben-Hur feels like it is trying way too hard to be an epic film. Every scene full of extras, giant sets, lavish costumes, and rich colors just screams "over-the-top".
The story at its core isn't a bad one, nor is the film bad in any respect. But it is tedious and I believe the above reason is part of the reason why.