Tough to narrow it down to one so here's a list
Elite (AMIGA/C64)
Magic Pockets (AMIGA)
Xenon2 (AMIGA)
Ultima Online (PC)
Wing Commander (AMIGA)
Privateer (PC)
Sonic (MEGADRIVE)
If I had to choose 1 to take with me to a deserted island then it would be Elite.
