I'll dare to participate, too exciting exersice to miss. List is extremely subjective and not include games which I haven't played. Also, one game per franchise only.
5 points:
XCOM: Terror From The Deep (1995, MicroProse). It just so happens I played the sequel first. When I met the original afterwards, it didn't impress me. Much more grim appearance and especially music themes are to my liking.
Heroes of Might and Magic III (1999, New World Computing). I'm very fond of the second game in series but gameplay wise third is just better.
Starcraft (1998, Blizzard). The game which showed me the world of competitive play and it drowned me even worse with release of WC3. Anyway, SC's a truly great game, one of the best, ever.
Prince of Persia (1989, Jordan Mechner). Besides the fact that it's great, defining and bla bla bla it's still enjoyable! Every few years I keep replaying it.
Dungeon Keeper (1997, Bullfrog Productions). Design of this game is phenomenally good. And it's such a joy to play. Sequel was very good too but like something was missing.
3 points:
Warcraft 3 (2002, Blizzard). The game is fantastic but despite one more race and the addition of RPG elements I consider it below SC.
Evil Genius (2004, Elixir Studios). Aesthetics and overall design are just excellent. The only decent "successor" of DK that I know of.
Doom (1993, id Software). As any of the above, it's still very enjoyable to play.
Quake (1996, id Software). Fucking great.
Subnautica (2018, Unknown Worlds Entertainment). Beatiful and not too tedious for a survival game. Outstanding.
1 point:
Sid Meyer's Civilisation V (2010, Firaxis Games). As much as I loved the older games (AC included), they're all kinda suck due to mass town spreading>all. The Vth finally got mechanics against it but got retarded AI as well so the game shines in MP only. Can't rate any higher.
The Long Dark (2017, Hinterland Studio Inc.). While the "main" story mode suck and still incomplite anyway, the main sandbox mode is glorious and able to give a really memorable experience.
This War of Mine (2014, 11 bit studios). Engaging.
Stardew Valley (2016, ConcernedApe). A true escapism.
Emperor: The Rise of the Middle Kingdom (2002, BreakAway Games, Impressions Games). Monumental.
Hotline Miami (2012, Dennaton Games). Feisty and fun.
Carmageddon (1997, Stainless Software). Pure joy.
Duke Nukem 3D (1996, 3D Realms). Another classic.
Oxygen Not Included (2019, Klei Entertainment). My kind of Asperger's.
Alley Cat (1984, Sinapse Software). Probably the very first PC game that I've played. Not the best start, consider how fine this game is. A follow-up to take that for granted and to discover so much shit games afterwards...