EDIT:
We use RetroArch now. See https://nhl94online.com/html/getting-started.php and scroll down to the Mac section.
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I don't have a Mac, so I can't really help.
Here are a few popular Mac emulators that you can use to play NHL'94. If you know of any more that are good, please post them.
Sega Genesis/Megadrive
Kega Fusion -- playoffs work, but no netplay?
Generator (Apparently has a bug that prevents playoffs from working)
Genesis Plus (Apparently has