Played Phoenix [Atari 2600] this week.
This is probably my favorite traditional fixed-shooter, even above classics like Galaga and Space Invaders. I just love how distinct the phases are, culminating in a mothership battle at the end of each loop. And the mechanics are perfectly simple - just shoot and dodge (along with a temporary shield that absorbs enemy fire, but can end up trapping you because it locks you in place while activated).
That's not to say I'm any good at this game - I was just happy to get a pitiful 20k score. Pattern-recognition and dexterity are the keys to success in any shoot-em-up, but early arcade-style shooters like Phoenix feel like they have a unique sort of unpredictability that's even more demanding on your twitch-reflexes. (And I, for one, have no such reflexes to begin with...)