I was there 2 years ago. I went inside one of the multi storey gaming places in Akihabara. The old school (90's and older) era games are a small section in one floor when there is 6 storeys of gaming.

That sounds like the Taito Station on the right side of the street. On the other side there is a Gigo with a whole floor for retro games, and Hey! that is focused almost only on retro games.