You need a separate encoder if you want to use it in all games.
The best current encoder is available from Groovy Game Gear.
It converts the 49-way signal so that it appears to the computer to be an analog stick.
The nice thing about this particular encoder is that it will also convert the signal so that it will appear as a 2-way, 4-way, rotated 4-way, or 8-way stick.
It also has a few other specialty modes.