Battle Nation is a great fanmade game based on an arcade classic by Namco called Battle City, which is in turn based on Atari's Combat.

Dig Dug is a great PC port of Namco's coin-op classic of the same name, ported by Atari.

Galaxian is another near-flawless conversion of coin-op classic for Atari.

Oh, those crazy Japanese console programmers.

One of the most loved arcade games, Pole Position is a watershed in arcade racing games and was THE game that set standard for all subsequent "checkpoint racers" (i.e.

Pole Position II is a decent EGA/VGA conversion of Namco's arcade hit of the same name.