Atwood's Law again.
Coincidentally, I've been looking at this https://github.com/paulscode/mupen64plus-ae/ for my phone, it works fine on my Android tablet.
Yes, it's true that Super Mario 64 is one of the easiest roms to get running as it uses relatively few features.
The format (z64 vs v64) shouldn't matter - I byteswap the file on load. I don't handle compressed roms though.
A few other roms that should boot: mario kart, wetrix, aeroguage, extreme-g, pilot wings, star fox. I haven't tested many others yet - let me know if you have success with anything else!
One thing to bear in mind: reload the page when you switch roms. There's some state I'm not resetting properly which breaks everything quite horribly. Sorry for the lameness - I'll try to get this fixed ASAP.
If you open the debug pane, you should get some debug output which gives you some clue as to why the rom failed to boot (usually unhandled memory accesses, unimplemented save format, unimplemented instruction, something like that). For the games that do boot, there are still some cpu bugs which prevent them from passing the CIC-chip's CRC check. E.g. GoldenEye and Zelda OoT both seem to fail in this way.
Running around in Mario 64 on a Celeron 233 with 3d being rendered in software blew my mind.
Edit: I took a look at the technical information on his blog[1] and found:
"It's still far from being playable. I mean, you can run around in Super Mario 64, but it's not particularly enjoyable. Various other games boot, but there are lots of bugs, graphics glitches and slowness. Realistically, I think it's going to be a long time before enough of these issues are fixed that n64js could be considered 'usable'."
Still, cool that he got it working at all.
[1]http://n64js.blogspot.co.uk/