Should I play System Shock 1 if I want to play System Shock 2?

You don't need to.

It's not mac only as far as I know, I didn't play the first game and loved the second one, looking back at the firtst one, I'm not sure I could go back to it.

Despite being a direct sequel to System Shock 1, System Shock 2 is sort of standalone. It only makes minor references to the events of SS1.

Or so I've heard.

Just checked community hub for SS2. They said you don't have to play SS1 to understand the story. Pretty much what happened in SS1 was told in SS2 intro.

I've heard only great things about SS2, but I've always wanted to play SS1 first.

Several times I've started SS1. Never have I finished it.

The controls are clunky and dated. It doesn't play nearly as well as any modern game. It's a CHORE to play.

....So trying to play it after playing SS2 would be impossible...

As others said: SS1 hasn't aged nearly as well as the sequel (even when it was new, it was considered somewhat clunky), and 2 starts of with a good recap of all you need to know from the previous one.

No need. It's a great game, back in the day i had difficulty to get into it too, (was used to playing doom) but after i did my vision of videogames changed drastically, and actually replayed it more times than ss2. It's also nice to hear and get to know the ss1 Shodan if you like the character, like if you enjoy glados you should really play both portals.