What the hell is up with the FDS, anyway? That has got to be the worst idea in the history of video gaming.
It's so lame that you can only play SMB2 (J) if you have a Disk System, because that is one piece of video game history I will never bother with.
I think it's an ok add on for the famicom still it's not perfect.
As turbo D mention the belt drive can go bad then you need to replace it.
Wich is one of the reason why i don't play it as much.
If any thing i have the, FDS as a collection peace heck i play the carts more then the disc.
Also there are "boots of SMB2" that can be found as well on cart for it and there was also the offiical release of, SMB2 for the GBA import only of corse.
FDS was simpley a cheap way for nintendo to get there games to the consumer nothing more.
While in the end... it was replace by carts once it got cheap and they could more with it.
You can read more about it here if you care
http://www.atarihq.com/tsr/fds/fds.html