Up until 6. Ng5 the game seems to be a common book posistion and haven't even been able to find a game online with 6. Ng5, so what am I missing and why is it not considered the best move instead of the common 6. O-O?
The line you give leaves Black with a fantastic position. Clearly better... I haven't even wasted my time putting it into an engine, I don't need to.
You're also 100% wrong about this being a book position. Why are you playing b5 so early? You don't have a reason and this is not the correct move order. If nothing else, it allows White to avoid the Marshall without having to avoid the 8.c3 line, by transposition.
I have spent the last hours trying to come up with a good defence to whites attack, and so far I haven't gotten anywhere. I have tried d5, and after e4xd5, Nxd3 instantly loses to Nxf7. After e4xd5 Nd4 d6 Nxb3 d6xc7 Qxc7 seems to leave white with a pawn up. I have tried playing with countless other variations, but black always gets stomped.
Up until 6. Ng5 the game seems to be a common book posistion and haven't even been able to find a game online with 6. Ng5, so what am I missing and why is it not considered the best move instead of the common 6. O-O?