I will not tell you anything, just give a bunch of screenshots (so that you can see how the games developed) and the opportunity to ponostalgate. All pictures are clickable, and a lot of traffic. Happy weekend!
Warcraft
Warcraft: Orcs and Humans, 1994

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Warcraft II: Tides of Darkness, 1995

Warcraft II: Beyond the Dark Portal, 1996. A new landscape view has been added.

Warcraft III: Reign of Chaos, 2002

Warcraft III: The Frozen Throne, 2003

World of Warcraft, 2004

After three additions: World of Warcraft: The Burning Crusade (2007), World of Warcraft: Wrath of the Lich King (2008) and World of Warcraft: Cataclysm (2010), the game is about the same:

Mario
Donkey Kong, 1981. Then Mario was not called Mario, but called Jumpman.

Mario Bros., 1983

Super Mario Bros., 1985

Super Mario Bros. 2, 1988

Super Mario Bros. 3, 1988

Super Mario 64, 1997. Before that, there were a whole bunch of different Tetris, tutorials and arcades with Mario, but for the most part they were adaptations of the game for different platforms (NES, VB, GB), other levels and occasionally minor improvements.

New Super Mario Bros. Wii, 2009

Super Mario Galaxy 2, 2010

Doom
Doom, 1993

Doom II: Hell on Earth, 1994. Almost nothing new, except a shotgun and more mobs.

Doom 64, 1997

Doom 3, 2004

Duke nukem
Duke Nukem, 1991

Duke Nukem II, 1993

Duke Nukem 3D 1996

Duke Nukem: Manhattan Project, 2002

Duke Nukem Forever, 2011

Civilization
Civilization, 1991

Civilization II, 1996

Civilization II: Test of Time, 1999. Added the ability to play for aliens and against them.

Civilization III, 2001

Civilization IV, 2005

Civilization IV: Colonization, 2008

Civilization V, 2010

Heroes of Might and Magic
Heroes of Might and Magic: A Strategic Quest, 1995

Heroes of Might and Magic II: The Succession Wars, 1996

Heroes of Might and Magic III: The Restoration of Erathia, 1999

Heroes of Might and Magic IV, 2002

Heroes of Might and Magic V, 2006

Might & Magic Heroes VI, 2011

Have a nice sunday evening!