I have tried playing GENS and it was decent, but for me personally, does not compare to SNES.
Two key things that put the SNES version way out in front of the GENS version is the player control and passing.
I don't care about framerate!
Also, I like the SNES controller and controls much better, along with the music and sound effects, the non-blue ice, as well as the goalie and checking animations.
Whenever I play the GENS version, I feel like I'm playing a suped up version of NHLPA 93 on SNES, with one-timers and minus the fighting of course. Whenever I play the SNES version, I feel like I'm playing a gift from God.
I really don't understand why the GENS version is more popular, but to each his own, I guess.