I think I like it because I don't expect it to answer all my questions. I love mystery and I personally like it when my mind goes wild with all the possibilities of what's going on and trying to make sense of it all. I hope they never explain the GMan, either. Would be weird if they explicitly stated in some set piece who he was. He's almost some kind of Entity like something out of a Arthur C Clarke novel that transcends time and space, using his abilities as some kind of Cosmological Security Consultant- dealing with 'situations' with assets of his own, bringing them around when needed. Takes no sides and yet sees everything at once due to time not being linear to his perception.
The rest of the story, with trans-dimensional beings compelled by unseen forces and an unknown, supposed galactic empire and how they go about colonizing systems is fascinating in Valves limited exposition style of storytelling that does wonders for immersion. Only in Half-Life 2 has there actually been more of a direction to the story, especially in Episode 2, but on the whole I really have no expectations for closure from the Half Life saga anytime soon- which is the way most things in life are.