The only emulator I ever had any success with on an 020 machine was ZXAM, the Spectrum emulator. This is available from the aminet, http://de.aminet.net
Generally, a computer needs to be 8x as powerful as the computer it is emulating to achieve a reasonable speed. The CD32 just doesn't have the processing power to pull off NES or Master System emulation at speed. It has pretty much the same processing power as the Mega Drive, and, in terms of audio and video, is less powerful than the SNES.
As for MAME, it might be possible to run some of the very basic ROMs at a decent speed, but current ports of MAME aren't optimised particularly well - it needs re-coding in m68K assembly to achieve worthwhile speeds, and no-one is likely to attempt that.