Wow, quite the list of oldies, but goodies above...including Odyssey The Complete Apventure (1980). That was a fun one 
These are 2 of the oldest I remember...
1) Pong- Except not played on a console, it was played on a TV that had the actual 12"x12" Printed Circuit Board atop the TV that converted it to a Pong Game.
2) and using a Radio Shack TRS Lvl 1 with 4k of memory that used a tape cassette drive to run programs...
Played Hammurabi, a farming buy/sell game. Managed food, and plots of land.
Also played some kind of space attack game with Klargons and Torpedoes on some kind of Battleship type map.
And while not the first PC games I played, (and to test other Oldie folks memories), anyone remember...
Midway, B-1 Bomber, Dneiper River Line, Tigers in the Snow, North Atlantic '86, Claim Jumpers (Think that was the name of an Avalon Hill game about mining the planets of the solar system), Escape from Rungistan,
and the old "Nuclear War"? not sure of title name, but played on a Battleship map, you had Cities (C), and could make Bombers(
, Missiles, Subs(S), and anti missiles(A). Pre-war, each turn you could either make 2 bases of any type (subs after 1960 or such), or make 1 base and conduct espionage which prevented a surprise attack, or Declare War.
Tactics were simple...If I Declared war the turn you made 2 bases, I'd get the first strike, but if you made 1 base and espionage, no first strike advantage., Missile were inaccurate but instant, Bombers were slower but almost never missed targets, and subs, once sortied, were invulnerable and could missile launch for the last parting shot.
...and all the standard Zork text games, the ones that lied to you...something like this
Computer- "Where do you want to go?"
Player. "West".
Computer- "You can't go West." "Where do you want to go?"
Player- "West".
Computer- "Ok, we lied, you can go West".
oh yeah, forgot Torpedo Fire- an SSI game in which to fire deck guns and fire torpedoes you had to know Trigonometry and calculate stuff using the Pythagorean (sp?)theory.
go go long term memory!!!
