20. Starflight (Binary Systems, 1986)
The followup to Blizzard's mega-hit Diablo, the second game in the franchise upped the ante in almost every way. Featuring faster gameplay, a choice of five new classes (seven in the expansion) each with their own variety of skill sets and equipment choices, and of course a plethora of new quests, items, bosses and challenges to undertake. It also featured multiplayer for up to eight simultaneous players, who could choose to tackle dungeons, gain levels or just duke it out in battles to the death. Other new features, like "Rune words" and the ability to combine items and reroll equipment properties would also become staples of other games in the genre. Once again, a major hit for Blizzard that continues to be fun even today. There are even a few killer fan mods available for those tired of the stock game.
15. Thief Gold (Looking Glass Studios, 1998)
14. Baldur's Gate II: Enhanced Edition (BioWare/Beamdog Software, 2013)
13. Ultima IV: Quest of the Avatar (Origin Systems, 1985)
12. Undertale (Toby Fox, 2015)
11. Fallout 2 (Black Isle Studios, 1998)