I only know Godot, so I can't say. Though I've never seen it performed. (Which I think is crucial with any theatrical work.)
"Not I" is a pretty impressive piece, imo, especially that performance by Billie Whitelaw. I remember seeing it on the TV in the 70s, and recalled it today. It's quite hypnotic.
And, oh yes, there's Krapps last tape, or something. Which rings a bell.
Beckett, I think, was one of those phenomenally clever people that you either like, or don't.