If you're the kind of player who appreciates solitaire games, this would do the trick... back in 1990.
One problem with Shanghai is that you only get a single formation so, once you beat it by clearing the table of all the pieces - and watching the dragon picture at the end - you pretty much saw the whole game. Fortunately, every new game distributes the pieces randomly, providing some replay value.
Another issue is that the game doesn't keep score or have any clock, so there's no incentive to go back and do better. This is clearly a game meant to pass the time and nothing else.
For its time, since the Game Boy was a recent console, and the whole portable gaming wasn't fully developed yet, this worked fine, but even by those standards you can't help but feel that Shanghai could've been more than it is. For instance, other Puzzle games for the GB, at the time, allowed you to build your own levels, or had a two-player mode, but none of that is present here.
On the bright side, Shanghai allows you to choose from 3 different background songs during gameplay, by simply opening a menu with the Select button, which is a nice touch other games should follow. All of them are pretty good for what a Game Boy can deliver, especially as an early generation title. Sound effects, however, are minimal.
Graphics are simple but effective, showing the pieces up close for optimal visibility. This forces the player to scroll the screen left or right when you first start a new game, but once the side pieces are clear the screen becomes fixed. Another nice little touch is the option to change the face of the pieces from their typical drawings (which may be hard to differentiate on a GB screen), to a more clear "letters and numbers" look - also available any time during gameplay, by way of the Select button.
Unfortunately, nowadays, this game is pretty much obsolete because you can easily find better versions of Mahjong Solitaire on the internet - most of them for free. Still, if you happen to own a GB and plan on playing this when you're at the doctor's lounge or at a bus stop, I'm sure this would definitely help the time fly.
The fact the game is so addictive is what makes it equally disappointing that you only get one way to distribute the pieces, can't create your own levels, and can not play with someone else - not even by keeping score so you could compare to your friends.
Time wasn't gentle with this one, true, but the addictive gameplay and the attention to detail in both sound and graphics make Shanghai a relatively good GB title for its time.