50. Jazz Jackrabbit (Epic MegaGames, 1994)
49. Magic: The Gathering (aka Shandalar) (Microprose, 1997)
Magic: the Gathering is the granddaddy of all collectible card games, and it began all the way back in the early '90s. As popular as it became, a number of video game adaptations would naturally follow, including an online game launched in 2002 that continues to this day and incorporates new expansions as they are released. But before all that started off, Sid Meier (yes, that Sid Meier) created a version of Magic that proved to be quite a bit of fun. Not only did it let you build your own decks to duel against computer opponents and feature extensive tutorials (with gloriously cheesy FMVs that combined CGI and live actors), but it even had a full-fledged RPG mode where the player tried to save the land from five evil mages, and make no mistake, it was an RPG; defeated opponents would give currency to let the player buy new cards, they would ante up new cards or clues to puzzles as a reward for victory, there were a number of dungeons to earn rewards from (usually in the form of temporary advantages for the next few duels), and one could even upgrade their own character with more starting Life Points and other advantages. There were even a few expansion sets (Spells of the Ancients, Duels of the Planeswalkers and the unofficial ManaLink) that added new card decks, online multiplayer support and fixed various bugs in the original release. Really cool stuff on the whole, and still surprisingly fun.
48. Out of This World (Delphine Software, 1991)
47. Shadowgate (Zojoi, 2014)
46. Ultima Underworld: The Stygian Abyss (Blue Sky Productions, 1992)
45. Sid Meier's Civilization V (Firaxis Games, 2010)
Civilization is doubtlessly one of the most popular and successful franchises associated with PC gaming and Sid Meier, and they're all quite good in their own ways, keeping the same basic underlying gameplay while adding their own mechanics and tweaks. 5 is my favorite one so far, overhauling the gameplay in numerous ways with things like "Social Policies" (cumulative bonuses that the player can purchase with Culture) and city-states that the player can curry favor with or conquer at their leisure. In addition, you can now achieve victory through military might, winning the space race, diplomacy, or just having the most developed culture to the point where all others bow in reverence to you. That, plus modding support, make it a game (and series) more addictive and replayable than almost any other strategy franchise I've seen. It's little wonder that Civ has been as popular as it has for well over two decades, even as it only recently started to gain a major presence on consoles.
44. The Oregon Trail (MECC, 1985)
If you're of a certain age, you probably remember playing this one in your school days, mostly because it's one of those rare educational games that was actually fun. In fact, it was actually rather like a roguelike in some respects - you picked one of three career paths (determining your starting money and score multiplier at the end), dealt with a lot of randomized hazards and splitting paths, and tried to reach Oregon with as many people still alive as you could. There were a lot of updates, remakes and rereleases over the years (still continuing to this day), but the fact that this game still remains popular despite having iterations going all the way back to 1971 speaks to its timeless charm.
43. AM2R (Some awesome fans, 2016)
42. Epic Pinball (Digital Extremes, 1993)
41. Fallout: A Post Nuclear Role Playing Game (Interplay, 1997)