Space Invaders is the first videogame I remember seeing.
[I never saw Pong... I saw it years later on the Atari 2600 and I've NEVER liked that original game although the Breakout spin-off is pretty decent.]
The first Space Invaders machine I saw was an upright model in an old, long-closed bowling alley in the town I grew up in. I have seen cocktail table/sit-down versions of it, too. Mostly at places like Pizza Hut which used to be big on cocktail videogame cabinets.
Can't recall if it was 1979 or 1980 when I first saw the game.
It was the first themed game that really made an impact and helped push millions of Atari 2600 VCS game systems into homes in the late 1970s and early 1980s. I know I owned copies of it on the Atari 2600 and the Atari 400/800 computer release.
Funny... about every 7-10 years I do play Space Invaders for a bit. Never for too long -- the game just isn't enough to hold my interest. I have to say, though, that I prefer Pac-Man and Donkey Kong among the early waves of Japanese videogames that hit big in the US. I'd have to say Donkey Kong, the ORIGINAL game, is probably my favorite Japanese videogame of this period.
A bunch of the early videogames would have been completely forgotten if not for MAME and other emulators. Space Invaders, Pac-Man, and Donkey Kong are still around and remembered well because of periodic re-releases of the original games, sequels, and remakes.