Well, my all time favourite game is Elite 2 - Frontier but I never made it to the Elite rank (somone here who has?).
Another favourite was Lotus 2 which I used to play against a friend in split-screen mode until he got so good that he became hard to beat...
Gauntlet 2 isn´t so bad either, I still play it on my A500 but it´s kind of dull when you don´t have anyone else to play it with.