The first one, yes. It's an awesome game and hailed as one of the best PC games for a very good reason.
Terror from the Deep is basically a reskin of the first one with the difficulty cranked up to over 9000. Only play it if you've already played the original and are desperate for more.
Apocalypse is a very polarizing game. Some people swear by it, claiming it's as good or even better than the original, others think it's crap. I'm mostly in the second camp, but it might be worth a look.
The spinoffs (Interceptor, Enforcer) are crap, avoid like the bubonic plague.
The AfterSomething series of remakes (Aftermath, Aftershock, Afterlight, etc.) are mediocre at best, but can kinda scratch the itch if you've exhausted main franchise.
In short, play the first one, then see if you want more.