I agree, as a former player of mainstream games I know this difference as much as anyone. I actually played doom, I played Quake when it first came out. This has been gone over to death, mainstream game companies do this for a living and they have around 100 people or so to do it. Audio games are made by someone in their spare time, and usually just one person. Even though GMA is nominally a "company" and they might appear as such from their web site they are really only a one man in his shed type operation.
Don't make the mistake of thinking audio games can replicate the efforts of entire teams at people who do this all day every day like ID software. Even other mainstream companies had trouble matching Doom, and as much GMA might have done no audio game developer has one tenth the development experience of any single mainstream games company employee that has worked on any real project.
cx2
-----
To live by honour and to honour life, these are our greatest strengths and our best hopes.