Right so I had a look around and apparently ripping sounds from GB/GBC isn't as easy as I expected. There's like no proper tools for it, the closest I could find was a Japanese application that doesn't work as people say it does.
But at least I managed to find something.
Here's a page containing heaps of GBS files, which are apparently what you get when extracting sounds from GB/GBC games. There are seriously heaps, I wouldn't be surprised if it had every single game. Anyway, here's the links for the GBSs of
SML1 and
SML2.
The format is kind of weird though, it isn't just a simple format that compresses encrypted sound files or something. In any case there's no program that can extract the sound straight up, the only way I've found to do it is by using a Winamp plugin to play them and output what it plays as a WAV. This works, but the problem is that it loops th music multiple times, as if you're in the game, fading at the end too. I mean it's possible to cut it with Audacity, but to do this so that it loops perfectly is really difficult. In any case it's not a proper rip.
There are however, sounds effects such as the level are possible to get pretty perfectly, since those don't loop and have a massive bunch of silence at the end I can cut off.
In short: I can get the sound effects such as level ending or losing a life, since those don't loop. I can't get level background music properly, I can try to get it so that it loops but it won't be as perfect as I'd like, and might not sound right. Also I haven't played these games so I don't know what other sound effects there are, but unfortunately I haven't found anything like jumping or proper gameplay sounds, only BG music and event jingles.