ColecoVision.

Aside from the fact that it has over 150 games available for it, of all sorts (Lord of the Dungeon and Fortune Builder, among many others), it is currently enjoying some pretty excellent homebrew support. Within the last year or so, we've seen Bejeweled, Space Invaders/Space Invaders Deluxe, and now, Sky Jaguar. That first and last both boost the variety of games available for the CV. It also has an excellent selection of really fine arcade-to-home translations.

However, unless Blockade Runner is any good, or Phaser Patrol is found and made available, Intellivision, with B-17 Bomber and Space Spartans, has the advantage in first-person shooters.