I think that for me, Seaman was one of the most incredible uses of the medium ever -- I have to say this with a very self-aware smile on my face, but I really do believe it to be true. The execution was far from perfect, but there is not a single game that has more effectively broken the fourth wall (in fact, the degree to which it breaks the fourth wall makes it a tremendous showpiece for the "Games as Art" argument), and it utilized its innovative exploitation of form in order to communicate a vast array of interesting ideas both directly and indirectly in dynamic accordance with the players' input.
The depth to which it explores the psychology of the player is rather stunning when closely examined -- you find that the creators actively exploit your discomfort toward the character. If you clam up around him, he kindly attempts to charm you in order to make you more sociable. If you make rude jokes about him, scoffing at the ridiculousness of his name and appearance, he responds with jeers that tease you for precisely the things that make you human.
The whole experience hits on linguistic, psychological, sociological, and existential themes so subtly that most never fully realize the way the creators change their perception over the course of the game. Obviously, there are the moments of legitimately interesting though sometimes surreal philosophizing on Seaman's end of the conversation, but the fact that the game makes you actually start to care for the well being of this thing that the average person sees as a freak through developing a personal relationship with it through language is actually fascinating, and a lot more groundbreaking than most people give it credit for.
It's fascinating enough that Seaman regards you, the human, as a freak, but his response when he asked if I thought he exists and I replied "No" is still just about the most unbelievable experience I've ever had playing a video game.
So! I'm ecstatic for the idea of a Seaman revival!