This poster is fairly mysterious.
It's status is currently: LOOKING FOR INFO.
It may move depending on what's found out. This is from the Sonic 1 era, it's an early item. The slogan at the bottom "To be this good takes AGES to be this good takes SEGA" was more frequently used in Europe area, but was also found on a few USA items. Next, notice the font for "Sonic" is not the usual one appearing in the logo, but a thinner font, sent in red, while the "the hedgehog" portion is the same.
This poster is fairly large, at least 22 inches long. Was it a retail display item, given to retail game shops by Sega to help advertise? Or, was it sold to the public as a regular item? It could also be a bonus or give-away at a trade show. The paper appears to be fairly heavy stock. The design is rather nice, with the Sonic art laid over the two backgrounds & large Sega logo. Have you seen this poster & can provide more info? Please write in for credit.