You may be a bit confused about why this game is such a big deal if you didn't grow up in the era of the Dreamcast, which is why I enjoyed the above video from VGS English explaining why Shenmue made such a big impression on them, and continues to be a favorite in the open-world genre.
Finding out what others like about a game is always more interesting than repeating the fact that you don't personally understand it, and this video does a good job of walking people through the warm feelings fans of the series continue to have for the game.
If you're curious about how the game looked, or at least an idealized version of it, you can check out the video below that shows the game running at 1080p at 60 frames-per-second via emulation. Beware, you may see some spoilers.
Sega, this would probably be a good time to release an updated version of the first two games for players curious about what they may have missed.