Four full hours with stiff and hammy acting sure makes for a tiresome experience. It's impressive in scale, but not in terms of storytelling. Times is spent on all the wrong things, and I bet an hour could be cut without it changing the main story one bit. I mean, 50 minutes in, Moses has barely had anything interesting to say, and no feelings towards him have been established...
Luckily it picks itself up when Moses is banished. The story and arc of Moses is much better handled, finally letting the audience join in on the experience. Still the dialogue and the acting is as hammy as ever. At least it provides some striking imagery, and some fine location work.
For a similar type of movie, watch the brilliant Ben-Hur instead. Superior in probably every department, and one the finest epics in the history of cinema.