Indeed, classifying Beckett's work with definitive terms is a challenge.  There are moments in the work where comedy does present itself, and there are equally challenging moments where pessimism reigns supreme.  In its articulation of the human condition, the play exposes that much of the human condition lies in between different polarities.  It is fairly impossible to draw one such judgment in a setting, but rather explore how the predicament of human beings might constitute different experiences at different moments.  There is a certain level of pessimism that is revealed at the ending when Godot defers his arrival for another evening.  While Beckett is making an existential statement on the human condition, one cannot deny that the notion of waiting and the paralysis that results is an integral part of the human predicament.  In this light, pessimism is an understandable experience on the part of the reader/ viewer.

In short,"Waiting for Godot"  is neither comic nor pessemistic. It is absurd.  Estragon and Vladimir wait and wait and wait for Godot. But what amounts to their waiting? Nothing. This play is a classic of "Theatre of the Absurd". It's philosophy is bleak regarding the human condition.  In addition, the style of writing that depicts that vision shows humans acting in a meaningless world, trying to make meaning. This theatre is based upon the philosophy of existentialism. For example Sisyphis, in mythology rolled the bolder up the hill forever. He had no choice regarding his life; he was doomed to do it forever.(his fate) However, he did have the choice over how he interpreted it. Other writers like Albert Camus and Jean-Paul Sartre were similar to Beckett in depecting an impersonal universe.