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.
18. Starflight (Binary Systems, 1986)
Ion Storm was a company as well-known for the names on its payroll as for its comically extravagant office space and outlandish development costs. But despite some questionable management decisions, they managed to turn out several high profile titles in their short existence. The one that easily stole the show was Deus Ex - a dystopian science fiction tale set in a world where every conspiracy theory imaginable is real. It was also an early example of a game where one's choices actually matter, with significantly different play styles depending upon the player's choice of skills, story events changing based on choices and even three different endings. A compelling dark tale in a surprisingly credible future, there's a good reason that it's the centerpiece of a meme: "Every time someone mentions Deus Ex, someone reinstalls Deus Ex. "
14. Thief Gold (Looking Glass Studios, 1998)
13. Ultima IV: Quest of the Avatar (Origin Systems, 1985)
12. Undertale (Toby Fox, 2015)
11. Fallout 2 (Black Isle Studios, 1998)