You would be hard-pressed to find a more influential game than David Braben's sprawling space-trading, wireframe-3D effort from 1984. It invented the space-sim genre, and as the first open-ended game, you could argue that the likes of World of Warcraft and Eve Online would never have existed without it.
Sadly, though, it was never followed up by anything remotely satisfying. Braben's company, Frontier Developments, took off, which sidetracked him; two putative sequels - Frontier: Elite II and Frontier: First Encounters - arrived in 1993 and 1995, but weren't a patch on the original. Braben, still as active as ever, has spoken about making a true, modern-technology sequel to Elite for decades now. Perhaps some day, somebody will shove a huge pile of money in his direction and tell him to abandon everything else.